• TABLE OF CONTENTS
HIDE
 Title Page
 Table of Contents
 Reasons for supplemental irrigation...
 What can be expected from home...
 Why do you want your system properly...
 Water sources for home irrigation...
 Testing the water supply
 Water quality for irrigation
 Sprinklers
 Micro-irrigation
 Bubblers
 Valves and controllers
 Backflow prevention
 Some rules of good design
 System management
 Scheduling to avoid drought...
 Scheduling by the accounting...
 References














Title: Irrigation of lawns and gardens
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00014491/00001
 Material Information
Title: Irrigation of lawns and gardens
Series Title: Circular
Physical Description: 16 p. : ill. ; 28 cm.
Language: English
Creator: Haman, D. Z ( Dorota Z )
Clark, Gary A
Smajstrla, A. G ( Allen George )
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: [1992]
 Subjects
Subject: Lawns -- Irrigation -- Florida   ( lcsh )
Irrigation -- Equipment and supplies -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 15-16).
Statement of Responsibility: Dorota Z. Haman, Gary A. Clark and Allen G. Smajstrla.
General Note: Title from cover.
General Note: "January 1992."
 Record Information
Bibliographic ID: UF00014491
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 001752720
oclc - 26977798
notis - AJG5677
 Related Items
Other version: Alternate version (PALMM)
PALMM Version

Table of Contents
    Title Page
        Title Page 1
        Title Page 2
    Table of Contents
        Table of Contents 1
        Table of Contents 2
    Reasons for supplemental irrigation of Florida lawns and gardens
        Page 1
    What can be expected from home irrigation systems
        Page 1
    Why do you want your system properly designed
        Page 1
    Water sources for home irrigation systems
        Page 2
        Page 3
        Page 4
    Testing the water supply
        Page 5
    Water quality for irrigation
        Page 6
    Sprinklers
        Page 7
        Rotary Sprinklers
            Page 8
    Micro-irrigation
        Page 9
    Bubblers
        Page 10
    Valves and controllers
        Page 10
    Backflow prevention
        Page 11
    Some rules of good design
        Page 12
        Refinement of the system
            Page 12
        Importance of sprinkler overlapping
            Page 12
    System management
        Page 13
    Scheduling to avoid drought stress
        Page 13
    Scheduling by the accounting method
        Page 14
    References
        Page 15
        Page 16
Full Text



January 1992


Circular 825


Irrigation of Lawns and Gardens

Dorota Z. Haman, Gary A. Clark and Allen G. Smajstrla
































Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida
John T. Woeste, Dean


r











































































Dorota Z. Haman, Associate Professor, Agricultural Engineering Department, University of Florida, Gainesville FL 32611; Gary A.
Clark, Associate Professor, Gulf Coast Research and Education Center, Bradenton, FL 34203-9324; and Allen G. Smajstria, Profes-
sor, Agricultural Engineering Department, Gainesville FL 32611.









Table of Contents

Reasons for supplemental Irrigation of Florida lawns and
gardens ...... .................................... 1
What can be expected from home irrigation systems ........... 1
Why do you want your system properly designed? ............ 1
Water sources for home Irrigation systems .......................2
Testing the water supply ......................... ......5
Water quality for irrigation ................................6.
Sprinklers ........................................... .7
Micro-Irrigation .........................................9.
Bubblers .............................................. 10
Valves and controllers ................................... 10
Backflow prevention .................................... .11
Some rules of good design ................................ 12
Refinement of the system .................................12
Importance of sprinkler overlapping ........................12
System management ................................... .13
Scheduling to avoid drought stress ........................13
Scheduling by the accounting method ...................... 14
References .......................................... 15












Reasons for supplemental
irrigation of Florida lawns and
gardens
Normal rainfall in Florida ranges from 52 to
approximately 60 inches per year. However, more
than one-half of the annual total rain falls from
June through September. During the winter and
spring, lack of rainfall may seriously affect lawn
and garden growth without supplemental
irrigation.

Often, droughts are thought of as long periods of
time, such as months or years without rain, but
Florida can experience drought conditions after
only a few days without rain. This is a result of the
very sandy soils in most of the state. Even during
the rainy season, evapotranspiration (ET) rates
may be high enough that irrigation of shallow
rooted crops is required in order to avoid excessive
water stress. Since the roots of most ornamental
plants and grass are quite shallow, these plants are
able to uptake the water stored in only the top 6 to
12 inches of the soil profile. Garden vegetables
may develop deeper roots and be able to obtain
water from depths of 18 to 24 inches. However,
Florida's sandy soils have very low water holding
capacities, and therefore the amount of water
stored in the root zone, and available to the plant,
is very limited. Consequently, to avoid water
stress, soil moisture must be replenished frequently
by natural rainfall or supplemental irrigation.

Many irrigated lawns, with frequent, high levels
of soil moisture content, would undergo stress from
a sudden restriction of water or elimination of irri-
gation. Some changes in water management, and
scheduling of supplemental irrigation, can improve
the drought resistance of turf and should be in-
cluded in lawn management. This process is called
drought conditioning. The objective of drought con-
ditioning is to grow a good quality lawn that will
survive on little or no supplemental irrigation. It
includes proper water application, good mowing
practices, fertilization, and pest control. Water
management aspects for lawns are discussed in
Extension Publication OH-63, Let Your Lawn Tell
You When to Water. Information on other aspects
of drought conditioning is included in IFAS Exten-
sion Publication OH-57, Preparing Your Lawn for
Drought.


What can be expected from home
irrigation systems
A typical homeowner is often unaware of what is
involved in the construction of a sprinkler or micro-
irrigation system. Often, it is thought that in buy-
ing an irrigation system one is buying complete
freedom from future watering problems. However,
even with a well-designed system, this may not be
true. A well-designed, good quality system will
significantly simplify watering, but it must be
managed properly. Proper management includes
proper operation, as well as regular maintenance.

A good irrigation system may be expensive, but
the investment should be repaid in time savings
and landscape maintenance. An irrigation system
should water a lawn and garden adequately and
efficiently. This can be accomplished with proper
design, properly selected good quality equipment,
and good management, regardless of the size and
complexity of the area which is irrigated. Major
reasons for unsuccessful irrigation systems include:
1) poor spacing of sprinklers/emitters, 2) under-
sized pipes, and 3) poor management.

Why do you want your system
properly designed?
Many home systems are not designed at all. An
installer may walk over the lot and place markers
at the approximate locations of proposed sprinkler
sites. This is not a good beginning to achieve
uniform and efficient water application.

A design should begin with a scaled map of the
area which includes existing buildings, trees,
shrubs, and sidewalks. The areas where water
should not be applied (examples: walls, sidewalks)
must be considered, as well as areas where irriga-
tion is desired. It is much easier to decide on paper
where to put certain sprinklers by considering their
areas of coverage, checking if sufficient overlapping
exists, and making sure that all of the area is
uniformly watered.

An existing water supply system must be exam-
ined to determine flow and pressure limitations.
The number of sprinklers which can be operated at
the same time should be calculated. Frequently, a
system must be divided into zones. Each zone is
designed to fit the water supply system by deter-
mining the most efficient way to connect sprinklers
into groups. The pipes must be sized based on the
water flow rate. Usually, several pipe sizes will be









Reasons for supplemental
irrigation of Florida lawns and
gardens
Normal rainfall in Florida ranges from 52 to
approximately 60 inches per year. However, more
than one-half of the annual total rain falls from
June through September. During the winter and
spring, lack of rainfall may seriously affect lawn
and garden growth without supplemental
irrigation.

Often, droughts are thought of as long periods of
time, such as months or years without rain, but
Florida can experience drought conditions after
only a few days without rain. This is a result of the
very sandy soils in most of the state. Even during
the rainy season, evapotranspiration (ET) rates
may be high enough that irrigation of shallow
rooted crops is required in order to avoid excessive
water stress. Since the roots of most ornamental
plants and grass are quite shallow, these plants are
able to uptake the water stored in only the top 6 to
12 inches of the soil profile. Garden vegetables
may develop deeper roots and be able to obtain
water from depths of 18 to 24 inches. However,
Florida's sandy soils have very low water holding
capacities, and therefore the amount of water
stored in the root zone, and available to the plant,
is very limited. Consequently, to avoid water
stress, soil moisture must be replenished frequently
by natural rainfall or supplemental irrigation.

Many irrigated lawns, with frequent, high levels
of soil moisture content, would undergo stress from
a sudden restriction of water or elimination of irri-
gation. Some changes in water management, and
scheduling of supplemental irrigation, can improve
the drought resistance of turf and should be in-
cluded in lawn management. This process is called
drought conditioning. The objective of drought con-
ditioning is to grow a good quality lawn that will
survive on little or no supplemental irrigation. It
includes proper water application, good mowing
practices, fertilization, and pest control. Water
management aspects for lawns are discussed in
Extension Publication OH-63, Let Your Lawn Tell
You When to Water. Information on other aspects
of drought conditioning is included in IFAS Exten-
sion Publication OH-57, Preparing Your Lawn for
Drought.


What can be expected from home
irrigation systems
A typical homeowner is often unaware of what is
involved in the construction of a sprinkler or micro-
irrigation system. Often, it is thought that in buy-
ing an irrigation system one is buying complete
freedom from future watering problems. However,
even with a well-designed system, this may not be
true. A well-designed, good quality system will
significantly simplify watering, but it must be
managed properly. Proper management includes
proper operation, as well as regular maintenance.

A good irrigation system may be expensive, but
the investment should be repaid in time savings
and landscape maintenance. An irrigation system
should water a lawn and garden adequately and
efficiently. This can be accomplished with proper
design, properly selected good quality equipment,
and good management, regardless of the size and
complexity of the area which is irrigated. Major
reasons for unsuccessful irrigation systems include:
1) poor spacing of sprinklers/emitters, 2) under-
sized pipes, and 3) poor management.

Why do you want your system
properly designed?
Many home systems are not designed at all. An
installer may walk over the lot and place markers
at the approximate locations of proposed sprinkler
sites. This is not a good beginning to achieve
uniform and efficient water application.

A design should begin with a scaled map of the
area which includes existing buildings, trees,
shrubs, and sidewalks. The areas where water
should not be applied (examples: walls, sidewalks)
must be considered, as well as areas where irriga-
tion is desired. It is much easier to decide on paper
where to put certain sprinklers by considering their
areas of coverage, checking if sufficient overlapping
exists, and making sure that all of the area is
uniformly watered.

An existing water supply system must be exam-
ined to determine flow and pressure limitations.
The number of sprinklers which can be operated at
the same time should be calculated. Frequently, a
system must be divided into zones. Each zone is
designed to fit the water supply system by deter-
mining the most efficient way to connect sprinklers
into groups. The pipes must be sized based on the
water flow rate. Usually, several pipe sizes will be









Reasons for supplemental
irrigation of Florida lawns and
gardens
Normal rainfall in Florida ranges from 52 to
approximately 60 inches per year. However, more
than one-half of the annual total rain falls from
June through September. During the winter and
spring, lack of rainfall may seriously affect lawn
and garden growth without supplemental
irrigation.

Often, droughts are thought of as long periods of
time, such as months or years without rain, but
Florida can experience drought conditions after
only a few days without rain. This is a result of the
very sandy soils in most of the state. Even during
the rainy season, evapotranspiration (ET) rates
may be high enough that irrigation of shallow
rooted crops is required in order to avoid excessive
water stress. Since the roots of most ornamental
plants and grass are quite shallow, these plants are
able to uptake the water stored in only the top 6 to
12 inches of the soil profile. Garden vegetables
may develop deeper roots and be able to obtain
water from depths of 18 to 24 inches. However,
Florida's sandy soils have very low water holding
capacities, and therefore the amount of water
stored in the root zone, and available to the plant,
is very limited. Consequently, to avoid water
stress, soil moisture must be replenished frequently
by natural rainfall or supplemental irrigation.

Many irrigated lawns, with frequent, high levels
of soil moisture content, would undergo stress from
a sudden restriction of water or elimination of irri-
gation. Some changes in water management, and
scheduling of supplemental irrigation, can improve
the drought resistance of turf and should be in-
cluded in lawn management. This process is called
drought conditioning. The objective of drought con-
ditioning is to grow a good quality lawn that will
survive on little or no supplemental irrigation. It
includes proper water application, good mowing
practices, fertilization, and pest control. Water
management aspects for lawns are discussed in
Extension Publication OH-63, Let Your Lawn Tell
You When to Water. Information on other aspects
of drought conditioning is included in IFAS Exten-
sion Publication OH-57, Preparing Your Lawn for
Drought.


What can be expected from home
irrigation systems
A typical homeowner is often unaware of what is
involved in the construction of a sprinkler or micro-
irrigation system. Often, it is thought that in buy-
ing an irrigation system one is buying complete
freedom from future watering problems. However,
even with a well-designed system, this may not be
true. A well-designed, good quality system will
significantly simplify watering, but it must be
managed properly. Proper management includes
proper operation, as well as regular maintenance.

A good irrigation system may be expensive, but
the investment should be repaid in time savings
and landscape maintenance. An irrigation system
should water a lawn and garden adequately and
efficiently. This can be accomplished with proper
design, properly selected good quality equipment,
and good management, regardless of the size and
complexity of the area which is irrigated. Major
reasons for unsuccessful irrigation systems include:
1) poor spacing of sprinklers/emitters, 2) under-
sized pipes, and 3) poor management.

Why do you want your system
properly designed?
Many home systems are not designed at all. An
installer may walk over the lot and place markers
at the approximate locations of proposed sprinkler
sites. This is not a good beginning to achieve
uniform and efficient water application.

A design should begin with a scaled map of the
area which includes existing buildings, trees,
shrubs, and sidewalks. The areas where water
should not be applied (examples: walls, sidewalks)
must be considered, as well as areas where irriga-
tion is desired. It is much easier to decide on paper
where to put certain sprinklers by considering their
areas of coverage, checking if sufficient overlapping
exists, and making sure that all of the area is
uniformly watered.

An existing water supply system must be exam-
ined to determine flow and pressure limitations.
The number of sprinklers which can be operated at
the same time should be calculated. Frequently, a
system must be divided into zones. Each zone is
designed to fit the water supply system by deter-
mining the most efficient way to connect sprinklers
into groups. The pipes must be sized based on the
water flow rate. Usually, several pipe sizes will be










required within a single system. It is much easier
to assure at the planning stage that the system will
provide what is expected rather than to attempt to
manage a poor installation.

The contractor should provide a detailed plan of
the irrigation system and specifications of all neces-
sary parts. The plan, including operational and
maintenance procedures, should be discussed with
the future owner. An example of an irrigation plan
and parts list is presented in Figure 1 and Figure 2.





PATIO



H- SRE LI'E s







Figure 1. A typical Irrigation plan for a home lawn.

home irrigation system. Water can be taken fm a













city water supply, private well, or from an open wa-
ter sourATce, such as a LAake or pond KL. If a city water
--.---- MILCl LATRALII R GE W OlKLICRII.OUAJTIER CONCLA



Figu preur 1. A typic lable n for a home lawn.e g w r


Water sources for home












to be purchased for the system, the well and pump
irrigation systems

There are several possible water sources for a
home irrigation system. Water can be taken from a
city water supply, private well, or from an open wa-
ter source, such as a lake or pond. If a city water
supply is used, or a well with a a already ex-
ists, the system should be designed for the flow rate
and pressure available from the existing water
source. If a well is to be drilled and a new pump is
to be purchased for the system, the well and pump
must be sized in the design process. For a surface
water supply the pump must be also sized during
the design process.

In Florida, well and pump permits from the local
water management district are required in some
cases. The local water management district should
be contacted for specific information on permitting.


PVC v Pi pv e INSERT
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I- PVC PIPE
INSERT REDUCING
MALE ADAPTER

'%s- I'T ADAPTOR
go $- -T ADAPTOR INSERT ELBOW
W COUPLING COMBINATION a
COUPLING REDUCING ELBOW
BUV S R I i'G INSERT TEE
WS TEE COMBINATION &
I"S TEE REDUCING TEE
uVs. C.v 'TREOUCER
TUCER INSERT COUPLING
I' I's rs-Z'T TH UC --
S 903 ELBOWW INSERT CROSS

*S*vT g PLASTIC
7 S T J'z REDUCER PIPC CLAMP
W"S 45* ELBOW POLY PIPE
I 1" S 45* ELBOW

J' R]: .1ISER




Vr'x_ RISER


Figure 2. Example of a parts list.

In addition, some municipalities require permits
and have restrictions on some wells.

The water supply must provide the volume of
water necessary to meet the irrigation require-
ments of the plants within each zone and within
the maximum time allotted for irrigation of that
zone. The flow rate of water available from the wa-
ter source, the water application rate, and the time
required for irrigation will determine the number
of irrigation zones and the size of each zone. For
example, if a lawn requires 1/2 inch of water every
second day and two hours are required to apply this
depth for each zone, the maximum number of zones
will be 24 for a system which operates 24 hours per
day. The practical number of zones would be much
smaller. Some systems are operated only at night
for no more than 8 hours/night. This amounts to 16
hours during two days. Therefore, if each zone
operates for two hours, the maximum number of
irrigation zones would be eight. A larger number
of zones would not provide sufficient time to deliver
1/2 inch of water every two days to the irrigated
area. The maximum number of zones for a given
type of system can be determined using the
following equation:









maximum number of zones = (T*R)/D

T = maximum time available for irrigation be
tween cycles (hours)
R = irrigation application rate (inches/hour)
D = irrigation depth per application (inches)

The zone size can be determined from the avail-
able water flow rate and the time allocated for the
irrigation of this zone. Assuming that the water
source is providing 20 gpm (2,400 gal during 2 hr)
and knowing that each acre-inch of water is equiva-
lent to 27,152 gal, the size of the zone can be calcu-
lated using the following equation:

2,400 gal
2,40 gl = .18 acre
27,152 gal/ac-in. 0.5 in

If the zone is larger than .18 acre, more than 2
hours are required to apply 0.5 in of water or a
larger flow rate from the water source is necessary.

Construction and development of a
well
An irrigation well should penetrate the water-
bearing formations as deep as needed to provide
the required flow rate while maintaining costs
within economical limits. In general, for small uses
like irrigation of lawns and gardens, wells will not
need to be as deep as wells for larger agricultural
applications. A 4-inch well usually will supply
enough water for a lawn irrigation system.

Florida water management districts provide
standards and criteria for construction, repair and
abandonment of wells. All wells within a district
must comply with these standards, regardless of
whether a permit for the well is required.

Water levels in the well may fluctuate during
different seasons. In addition, the water level is
lower during pumping due to the drawdown effect.
This level should be known to assure that the pump
will be able to lift the water at all times. For more
information on annual cycles and long-term trends
in water levels the water management district
should be contacted.

A new well should be tested to obtain the rela-
tionship between capacity (or discharge) and draw-
down within the well. The testing procedure
involves pumping the well at various capacities or
discharge rates and measuring the drawdown in
the well at each rate. Such information is


necessary for the proper selection of a pump for a
given well.

The contract for well drilling should include well
development and testing, and it should be a written
agreement between the prospective owner and the
well driller. For more information on well drilling
and development see IFAS Circular 803, Water
Wells for Irrigation Systems.

Pump selection
The pump selected for an irrigation system must
be able to provide the necessary flow rate at the op-
erating pressure required for each irrigation zone.

This involves selecting a pump that can move
the design flow rate of water from the drawdown
level in the well or the low water level of a surface
water supply to the level of the irrigation system,
produce enough pressure to overcome friction losses
in the system (from water flow through pipes, fit-
tings, risers, valves, etc.), and provide the specified
pressure for the sprinklers or emitters. Any signifi-
cant changes in topography must also be accounted
for as pressure losses or gains.

Each pump design is unique with respect to the
flow rate (discharge) provided and the pressure
(head) which may be developed. As the flow rate is
restricted, the discharge pressure (head) increases.
This relationship is generally expressed as a pump
head-capacity curve. A typical set of pump curves
is presented in Figure 3. In addition to the head-
capacity curve, the relationships between the
capacity and efficiency, and capacity and required
horsepower are presented in the same figure.

TDH-TOTAL DYNAMIC HEAD
zmo EFF EFFICIENCY
BHP- BRAKE HORSEPOWER


so NOTE. THIS PUMP WILL PUMP
520GPM AT 140FT
OR APPROXIMATELY
60PSI AT MAXIMUM
EFFICIENCY OF 72/o% 00
70



< 40
~ n,-
t,.-


CAPACITY, G.P.M.
Figure 3. A typical pump performance curve.









The three most common types of pumps which
are used for irrigating lawns and gardens are: sur-
face centrifugal pump, jet pump, and submersible
centrifugal pump. These pumps are discussed
briefly below. More information on pumps can be
found in IFAS Circular 832, Pumps for Florida
Irrigation and Drainage Systems.

Surface centrifugal pumps
In centrifugal pumps energy is imparted to the
fluid by the centrifugal action of an impeller. The
velocity head imparted to the fluid by the impeller
is converted into pressure head by means of a
volute case (Figure 4).





I oischorge
Impeller ch

Housing or Volute
"-Suction Pipe
Foot Volvo


Strainer

Figure 4. Centrifugal pump.

Centrifugal pumps placed on the surface have
limitations in the height to which they can lift wa-
ter by suction. The practical lift for a centrifugal
pump is approximately 15 to 20 feet. Therefore, if
the water level with respect to the pump is deeper
than this, due to drawdown or other causes, the
water column may separate, resulting in a loss of
pump prime. In these cases a different type of
pump such as jet or submersible pump may be
required.

Various sizes of centrifugal pumps provide dis-
charges from a few to several thousand gallons per
minute (gpm) at pressures required for irrigation
system operation. These pumps are usually
designed to provide efficient operation over a wide
range of pump speeds and discharge rates. Surface
centrifugal pumps can also be offset from the well
which may be convenient.

However, most centrifugal pumps can lose their
prime when turned off. A foot valve installed at
the end of the suction pipe helps to maintain the


suction pipe full of water during off cycles, such
that pump prime is maintained.

Jet pumps
A jet pump consists of a pump (usually centrifu-
gal) and a jet or ejector assembly (Figure 5). The
jet assembly can be located in the pump for shal-
low-well units or in the well for deep-well units.
The pump forces a portion of the discharge water
through the nozzle and venturi of the jet-assembly.
The rest of the water pumped is supplied to the dis-
tribution system. The practical lift of this pump is
approximately 22 feet for a shallow-well jet and up
to 85 feet for a deep-well jet. The amount of water
that must be provided to the jet increases as the
level of the water surface in the well decreases. At
a lift of 50 feet approximately 50% of the water
pumped is provided to the jet. Jet pumps can pro-
duce a high capacity flow at low head. Their disad-
vantage is a low operating efficiency because of the
need to recycle water to the jet.


Pipe


Figure 5. Jet pump with jet assembly in the well for deep well
applications.

Submersible centrifugal pumps
Submersible centrifugal pumps have one or more
impellers mounted close together on a single verti-
cal shaft, and the impellers and power unit (electric
motor) are encased in a housing which is located
below the water surface. Each impeller, its diffuser


4


__ __










(guide vanes to the next impeller), and housing is
called a stage (Figure 6). A 4-inch or larger well
casing is required for submersible pumps. Any re-
pair to the pump or motor requires removal from
the well, making service difficult. Service require-
ments of these pumps and motors are generally
minimal; however, in Florida, it may increase due
to frequent lightning problems. Because submers-
ible centrifugal pumps can lift water up to 1,000
feet, they are adaptable for use in deep wells.


STAGE


NYLON
/ROPE
ELECTRICAL
CABLE





PUMP


DFFUSER
IMPELLER
BOWL

WATER INLET
SCREEN
SEALS AND
BEARINGS

MOTOR




-BEARING


-OtL
[L RESERVOIR
WELL
CASING

S0 WELL
-SCREEN

Figure 6. Submersible multi-stage centrifugal pump.


Testing the water supply


The water supply for an irrigation system should
be tested. Testing involves determining the flow
rates produced against different pressures. The as-
sembly presented in Figure 7 is a tool which can be
used to test a pump or municipal water supply line.
If a flow meter is not available, a graduated bucket
and a stop watch can be used to determine the flow
rate. A globe valve or gate valve may be used to
vary the flow rate.


PRESSURE
GAUGE
REGULATING
FLOW METER 'L


FLOW ... .....

Figure 7. An assembly to measure flow rate versus pressure
from a water supply.

An initial pressure measurement should be
made with the valve closed. Then, the flow rate
should be gradually increased by opening the valve
in small increments. The system should equilibrate
for several minutes at each increment before
recording the pressure and the flow rate. This
process should be continued until the valve is fully
open. It is important to note that the pressure
reading is not necessarily the pump pressure, but is
the pressure of the system at the point of measure-
ment. This should be as near the point where the
irrigation system will be connected as possible.

A table similar to the following one should be
created:
pressure (psi*) flow rate (gpm*)

60 0
50 3
30 6
20 10
5 15
*psi: pounds per square inch
*gpm: gallons per minute

Note: Your numbers in both columns will differ
from the numbers in this example.

By graphing these data, Figure 8 is produced.
This is the calibration curve for the water supply.
It allows the pressure to be determined for any
given flow rate and vice versa. For example, if an


60
50
40
30
20
10


0 3 6 9 12 15
FLOW RATE (GPM)
Figure 8. Flow rate/pressure relationship for the irrigation
system.


5


DGCHARGE









irrigation system requires 9 gpm, only 22 psi will
be available at this flow rate. Alternatively, if 35
psi is required at the entrance of the irrigation
system for components to operate properly, then
only 5 gpm is available at this point.

The pressure of municipal water supplies fluctu-
ates during the day. During the times of low water
demand, such as late night or very early morning
hours, the water pressure is much higher. This
time may be the best for operation of the irrigation
system. If the water is supplied by a pump, Figure
8 should be similar to the pump curve provided by
the pump manufacturer. However, even if the
manufacturer's pump curve is available, it is advis-
able to run this test to examine the pump perfor-
mance, which may differ with particular conditions
of installation. A specific pump may not be as
efficient as presented on the manufacturer's curve,
usually due to installation. For efficient pump per-
formance well casing diameter should be at least
one nominal pipe size larger than the pump size for
a submersible pump. This allows for clearance dur-
ing installation and free water flow into the pump.
However, due to the additional cost, frequently a
4-inch pump is placed in a 4-inch casing in small
irrigation systems. Pump performance may change
and it decreases with wear, especially if the pump
has been used for a period of time.

Water quality for irrigation
Water quality of the water source may affect the
design of the irrigation system. In general, water
quality problems can be classified as physical, bio-
logical, and chemical. Physical problems relate to
mineral particles of sand, silt, and clay present in
the water source. Chemical problems are associ-
ated with high levels of soluble salts, calcium, mag-
nesium, bicarbonate, iron or manganese, which can
precipitate from the water, causing clogging or un-
desirable staining; or low pH (acidic water), which
can corrode metal parts. In shallow wells and sur-
face waters in Florida, biological problems are quite
often encountered. The presence of various
microorganisms, algae, and fungi can create main-
tenance problems in irrigation systems.

If the water for a home irrigation system is from
a municipal line, then water quality should not be a
major problem. This water has already been
treated for human consumption under require-
ments which are more restrictive than those for
irrigation water. All bacteria, part of the iron,
manganese, and other potential problem causing
minerals have already been removed. Filtration


may still be necessary for some systems, but the
type of selected filters may be much simpler.

Filtration and sometimes water treatment may
be necessary depending on the type of irrigation
system used and the water source (well, pond,
river, or canal). Sprinklers can be damaged by
physical contaminants such as sand and silt. Also,
flows may be restricted in lines or sprinklers by
chemical precipitation of calcium carbonate
(CaCO3) or by a buildup of biological slimes associ-
ated with sulfur or iron. Other chemicals or ele-
ments in the water may cause aesthetic problems.
The presence of iron and/or manganese can create
staining problems of walls and sidewalks when the
water is allowed to come in contact with them.

Poor quality water can create more problems in
micro-irrigation than in sprinkler irrigation. In
micro-irrigation water is delivered to the plants
through emitters which use small orifices or long
flow paths with small diameters. These small
openings are necessary to deliver the small flow
rates characteristic of these systems. Water qual-
ity management is generally necessary in the man-
agement of micro-irrigation systems. Clogging of
emitters may result from physical, chemical, and
biological contaminants.

In general, water to be used in a micro-irrigation
system will require filtration and often additional
treatment. Even with city water a 200 mesh filter
is recommended. Careful evaluation of irrigation
water and adequate water quality testing can help
to determine which of the preventive methods will
be most effective and reduce future maintenance
problems.

Clogging problems will vary with and within the
sources of irrigation water. Generally, the water
sources can be grouped into surface water, shallow
wells, and deep wells. These are in addition to the
city or other public water supplies.

An irrigation system using surface water will be
prone to biological and physical clogging. However,
chemical precipitation is normally not a major
problem in systems using surface water supplies.
Chemical precipitation is more common with the
groundwater supplies.

Physical clogging relates to mineral particles of
sand, silt, and clay which can aggregate in lines
and are large enough to clog the emitters. In the
limerock Floridan aquifer small particles of lime


6









scale are frequently encountered and may be
pumped through the system as well. Physical
clogging can be associated with all of the aforemen-
tioned water sources. Therefore, filtration is rec-
ommended and is generally necessary. It is recom-
mended that strainers be used in the sprinkler
irrigation systems and finer filtration (depending
on the emitters used) in micro-irrigation.

Chemical precipitants in the irrigation system
are often due to naturally occurring compounds.
Waters containing high levels of soluble salts,
calcium, magnesium, bicarbonates, iron, or manga-
nese can all be associated with chemical precipita-
tion. Chemical precipitation is usually found in
irrigation systems using groundwater. Chemical
treatment such as acid injection may be required to
prevent clogging of systems using water which has
a high potential of chemical precipitation.

Biological clogging due to algae cells and fila-
ments, their residues, and iron and sulfur com-
plexes are the major problems associated with
surface water and some groundwater sources,
especially with micro-irrigation systems. Residues
of decomposing algae can accumulate in lines, emit-
ters, and micro-sprinklers. This residue, consisting
of ruptured cells which forms soft non-sticky depos-
its, can collect iron and support the growth of iron
bacteria or other slime-forming bacteria. These
growths may clog systems or restrict flows, necessi-
tating periodic treatment such as chlorination.

Different filtration methods for micro-irrigation
systems are discussed in IFAS Fact Sheets AE-61,
Screen Filters in Trickle Irrigation Systems and
AE-57, Media Filters in Trickle Irrigation Systems.

Sprinklers
A sprinkler is an assembly which is attached to
the pipe system and used to disperse water over a
lawn, flower bed, or garden area. There is a wide
variety of types and styles of sprinklers. They
range from quite simple to relatively complex de-
vices. It is important to select the correct sprinkler
for a given application. Precipitation rate, operat-
ing pressure, and diameter of coverage are very
important in the design and selection process.
Sprinklers can generally be classified as spray
heads or rotary sprinklers.

Spray heads
A spray head has a fixed nozzle with an orifice
which results in water distribution in the form of a
fine spray. The extremely wide variety of nozzles


can facilitate different applications. The nozzle can
be easily removed and replaced. In general, a 15-30
psi pressure is required for operating spray heads.
Spray heads can be classified into bed spray head,
lawn spray heads and shrub spray heads. Bed and
shrub spray heads are usually stationary, where
lawn sprays can be either stationary or pop-up
types.

A bed spray head emits a small, flat or extremely
low-angle spray. The distance of coverage ranges
from 18 inches to 5 feet depending upon the spray
head design and the system operating pressure.
Bed spray heads are used in small restricted bed
areas and narrow planter boxes (Figure 9a).


Figure 9a. Bed spray heads.


FULL CIRCLE FULL CIRCLE
WITH CAP FLAT SPRAY
Figure 9b. Stationary lawn spray.

Stationary or surface lawn spray heads are short
mushroom-shaped sprinklers without moving parts
(Figure 9b). Stationary lawn spray heads are usu-
ally used in areas where minimum initial installa-
tion cost is a major factor. They are used in small
areas where rotary sprinklers are too large. They
are also selected in areas where blowing sand could
damage the mechanism of a sprinkler with moving
parts. Depending on the area to be covered, differ-
ent spray patterns can be selected. Spray heads









can be purchased in coverage patterns of 360,
1800, 0, or less. They can also have different ge-
ometries of coverage, such as circles or rectangles.
Because of these versatile patterns, spray heads
are ideal for small, odd-shaped areas.

Pop-up lawn spray heads are those which raise
the nozzle above the surrounding grass during op-
eration then drop down to the level of the ground
when not in use (Figure 9c). The pop-up feature
minimizes the need for trimming the grass around
the heads and at the same time improves water
distribution since the head is high above the grass
when in operation. Pop-up spray heads are usually
spring-operated and require a certain pressure
level to operate the pop-up mechanism. Operation
of the pop-up mechanism may be a problem where
the water contains large amounts of sulfur, iron, or
alkalines. These minerals are often present in
Florida's well water and they can cause failure to
pop-up moving parts by promoting chemical depos-
its or bacterial slime growths. A pop-up mecha-
nism can also be damaged by sand pumped through
the system.


Rotary sprinklers
Rotary sprinklers are designed to disperse water
in an arching stream-type spray pattern. Due to
the rotation of the sprinkler, a circular area is irri-
gated. Small rotary sprinklers usually use one
nozzle, while large sprinklers frequently use two
nozzles to accomplish uniform distribution (Figure
9d). The pattern of coverage for a rotary sprinkler
can be a full circle or a part circle. Rotary sprin-
klers are generally used for applying water to
larger areas and require operating pressures of 25
to 80 psi.

DRIVER ARM SPRING
IMPACT OR
DRIVER ARM



NOZZLE---- ----- BODY


HOUSING THREADS- TO RISER
,..,t"---SPINDLE WASHER


IMPACT DRIVEN ROTARY
SPRINKLER


DOWN POSITION


NOZZLE


UP PosmON
Figure 9c. Pop-up spray head.


Average precipitation of spray nozzles is rela-
tively high, approximately 1 in/hr. These nozzles
are used for rapid watering of lawns. However, use
on steep slopes and heavy clayeyy) soils may result
in runoff. Therefore, all irrigated areas of the
system should be examined for proper selection
and location of nozzles to avoid runoff.

Other nozzles include shrub sprays which are
usually specially made nozzles mounted directly on
permanent risers above the foliage of the shrub.
Generally, they are smaller in size than the nozzle
produced for pop-up lawn sprinklers. These nozzles
are used to apply water to all planted areas where
the height of the riser will depend on the applica-
tion and characteristics of the sprayer nozzle.


GEAR DRIVEN ROTARY
SPRINKLER
Figure 9d. Rotary sprinkler.

Stationary and pop-up types are available in
both impact and gear-driven models. Gear driven
models are usually more expensive but they provide
a constant speed of rotation which increases unifor-
mity of water application. In addition, the rotating
mechanism is usually well protected and often does









Table 1. Nozzle discharge in gallons per minute at 100% efficiency.
Nozzle diameter in inches
Pressure
psi 1/16" 5/64" 3/32" 7/64" 1/8" 9/64" 5/32" 11/64" 3/16" 13/64" 7/32"

20 0.52 0.81 1.17 1.59 2.09 2.65 3.26 3.92 4.69 5.51 6.37
25 0.58 0.90 1.31 1.78 2.34 2.96 3.64 4.38 5.25 6.16 7.13
30 0.64 1.00 1.44 1.96 2.56 3.26 4.01 4.83 5.75 6.80 7.85
35 0.69 1.08 1.55 2.11 2.77 3.50 4.31 5.18 6.21 7.30 8.43
40 0.74 1.15 1.66 2.25 2.96 3.74 4.61 5.44 6.64 7.80 9.02
45 0.78 1.22 1.76 2.40 3.13 3.99 4.91 5.91 7.03 8.30 9.60
50 0.83 1.29 1.85 2.52 3.30 4.18 5.15 6.19 7.14 8.71 10.10
55 0.87 1.36 1.94 2.63 3.46 4.37 5.39 6.48 7.77 9.12 10.50
60 0.90 1.40. 2.03 2.76 3.62 4.50 5.65 6.80 8.12 9.56 11.05


not come in contact with water. This protection
extends the life of the sprinkler.

Nozzles
The nozzle is that part of a sprinkler which actu-
ally distributes the water. It is the discharge open-
ing or orifice used on a sprinkler to control the vol-
ume of discharge, distribution pattern, diameter,
and droplet size. The volume of discharge from the
sprinkler is primarily a function of nozzle size and
pressure. Wetted diameter is a function of nozzle
size and pressure, but it is also greatly affected by
the type of sprinkler.

Generally, specifications of different nozzles are
provided by the manufacturer. However, if this
information is not available, the discharge volume
of a particular sprinkler can be estimated from the
size of the nozzle and the operating pressure
(Table 1).

Micro-irrigation
In micro-irrigation systems water is distributed
through emitters which are placed along the water
delivery pipe. Water is applied in the form of
drops, tiny streams, or miniature sprays. This type
of irrigation system operates under relatively low
pressures (6-30 psi) and can deliver water, nutri-
ents, and other chemicals directly into the root zone
of the plant. Micro-irrigation can be managed to
apply small quantities of water and/or chemicals to
precisely match evapotranspiration and nutrient
demands.

Micro-irrigation emitters use small orifices or
long flow paths with small diameters to deliver low
flow rates of water typical of this type of irrigation


Long Bubbler
Path on riser





Spray cic::
Jet Inline


Pressure
( & Compensating

LINE SOURCE EMITTERS

Double Path

Figure 9e. Types of emitters.

system. Several different types of emitters are
presented in Figure 9e.

The discharge rate of an emitter must be consid-
ered in the selection process to ensure that the
device can supply the required amount of water
within a reasonable time. For example, a
homeowner may have some trees with a daily water
requirement of 40 gallons per day and only 2.5
hours available for irrigation time. Then, the mini-
mum discharge rate to each tree must be 16 (40/
2.5) gallons per hour (gph). Emitters associated
with micro-irrigation systems typically have dis-
charge rates which vary from 0.5 to 2.0 gph for
drip-type emitters up to 5 to 35 gph for the spray
and mini-sprinkler type emitters. Therefore, in the
above example, eight 2.0 gph drip emitters, two 8.0


9








gph, or one 16.0 gph spray or mini-sprinkler would
have to be used for each tree.

Micro-irrigation systems are very suitable for ir-
rigation of trees, shrubs, flower beds, and all kinds
of small, restricted areas. They are not practical
for irrigation of large lawn areas, because water
does not distribute very well in the lateral direction
in Florida's typical sandy soils. This poor lateral
movement requires a very close spacing for drip-
type emitters to provide a uniform distribution of
water. More information on micro-irrigation
systems can be found in IFAS publication AE-24,
Principles of Micro Irrigation.

Bubblers
A bubbler head is designed to flood or soak a
restricted area where even a small spray might be
objectionable. Because bubblers operate under low
pressure and cover very small areas adjacent to the
plant, they are often included as a micro-irrigation
device. All types of bubblers operate under rela-
tively low pressures (1-10 psi). However, their flow
rates are relatively high (approximately 60 gph)
when compared with other micro-irrigation emit-
ters. Due to these characteristics the orifices of
bubblers are relatively large and less prone to clog-
ging. Bubblers are used in small pockets in "living
patios" or for special plants which should not have
water applied to the foliage (Figure 9f). The
"spider" type of bubbler distributes water over a
slightly larger area by several small flowing
streams (Figure 9g) and is useful under extremely
dense foliage. Distribution of water from the bub-
bler is determined by the distribution characteris-
tics of the soil. Lateral movement of water in sandy
(light) soils is small compared to more clayey
(heavy) type soils. Since the water is applied at the
high flow rate, it ponds around the plant. Due to
this ponding, the distribution of water in the root
zone is improved for a sandy soil, as compared with
the drip emitters. For clayey soils, water intake
rates are low; therefore, to reduce runoff losses, it
may be necessary to construct small containment
dams around the bubbler.

Valves and controllers

Valves
Valves are devices which are used for controlling
the flow of water in an irrigation system. There is
a wide variety of different types of valves which are
used for many different purposes. Valves can be


Figure 9f. Bubbler (flood type).


Figure 9g. Bubbler (spider type).


simple and manually operated, or more complex
with automatic operation.

A common type of manual valve is a gate valve
which is usually used as the main shut-offvalve
(Figure 10a) because of its low head loss when fully
open and slow closing characteristics. Opening of
the system too quickly may result in water surge
and water hammer, causing damage to pipes and
fittings.


Figure 10a. Gate valve.

Manual control valves such as globe valves (Fig-
ure 10b) are sometimes used for flow regulation
into a zone. Their design results in significant
pressure loss. Ball valves (Figure 10c) are some-
times used as on/off valves for different zones of
sprinklers. However, they should be used with


10








gph, or one 16.0 gph spray or mini-sprinkler would
have to be used for each tree.

Micro-irrigation systems are very suitable for ir-
rigation of trees, shrubs, flower beds, and all kinds
of small, restricted areas. They are not practical
for irrigation of large lawn areas, because water
does not distribute very well in the lateral direction
in Florida's typical sandy soils. This poor lateral
movement requires a very close spacing for drip-
type emitters to provide a uniform distribution of
water. More information on micro-irrigation
systems can be found in IFAS publication AE-24,
Principles of Micro Irrigation.

Bubblers
A bubbler head is designed to flood or soak a
restricted area where even a small spray might be
objectionable. Because bubblers operate under low
pressure and cover very small areas adjacent to the
plant, they are often included as a micro-irrigation
device. All types of bubblers operate under rela-
tively low pressures (1-10 psi). However, their flow
rates are relatively high (approximately 60 gph)
when compared with other micro-irrigation emit-
ters. Due to these characteristics the orifices of
bubblers are relatively large and less prone to clog-
ging. Bubblers are used in small pockets in "living
patios" or for special plants which should not have
water applied to the foliage (Figure 9f). The
"spider" type of bubbler distributes water over a
slightly larger area by several small flowing
streams (Figure 9g) and is useful under extremely
dense foliage. Distribution of water from the bub-
bler is determined by the distribution characteris-
tics of the soil. Lateral movement of water in sandy
(light) soils is small compared to more clayey
(heavy) type soils. Since the water is applied at the
high flow rate, it ponds around the plant. Due to
this ponding, the distribution of water in the root
zone is improved for a sandy soil, as compared with
the drip emitters. For clayey soils, water intake
rates are low; therefore, to reduce runoff losses, it
may be necessary to construct small containment
dams around the bubbler.

Valves and controllers

Valves
Valves are devices which are used for controlling
the flow of water in an irrigation system. There is
a wide variety of different types of valves which are
used for many different purposes. Valves can be


Figure 9f. Bubbler (flood type).


Figure 9g. Bubbler (spider type).


simple and manually operated, or more complex
with automatic operation.

A common type of manual valve is a gate valve
which is usually used as the main shut-offvalve
(Figure 10a) because of its low head loss when fully
open and slow closing characteristics. Opening of
the system too quickly may result in water surge
and water hammer, causing damage to pipes and
fittings.


Figure 10a. Gate valve.

Manual control valves such as globe valves (Fig-
ure 10b) are sometimes used for flow regulation
into a zone. Their design results in significant
pressure loss. Ball valves (Figure 10c) are some-
times used as on/off valves for different zones of
sprinklers. However, they should be used with


10









caution, since their quick operation may result in
water hammer.


Figure 10b. Globe valve.


OPEN
Figure 10c. Ball valve.


CLOSED


Irrigation systems with automatic control use
automatic valves for opening and closing of differ-
ent irrigation zones. Automatic valves can be clas-
sified into two major groups: electrical valves and
hydraulic valves.

Small irrigation systems for lawns and gardens
almost exclusively use electric types of valves. It
is very important to match the output of the
controller with the requirements of the type of
valves used in the irrigation system. For safety
reasons, 24 volts AC should be used for electrical
solenoid irrigation valves. Power is transmitted to
the valves through underground wires (for electric
valves) or control tubing (for hydraulic valves).

The other major distinction among automatic
valves is the position which a valve assumes if the
power from the control mechanism is interrupted.
Some valves close when power is not supplied and
they are called "normally closed." Other types of
valves remain open under no power conditions and
are called "normally open."

The other type of valve frequently used in all
irrigation systems is a check valve. Check valves
are used to allow water to flow in only one direction
(Figure 10d). These simple valves are useful for


A. B.
SPRING-LOADED CHECK VLVE SWING CHECK VALVE
Figure 10d. Two types of check valves.

restricting backflow of water from the irrigation
system to the water source.

Various valves are discussed in detail in IFAS
Circular 824, Valves for Irrigation Systems. A
reader interested in valve construction, applica-
tions, advantages, and disadvantages should
consult the above publication.

Controllers
Controllers can be simple on/off timer switches
which operate one or more remote automatic
valves, or they may be sophisticated computers
with many stations and variable programming.
Sophisticated controllers can control many valves,
allowing for operation at any time of day or night,
with individual scheduling for each valve. Some
controllers allow for programming of various irriga-
tion schedules for up to two weeks.

A controller may include a soil moisture measur-
ing device. This type of arrangement allows for au-
tomatic irrigation scheduling in response to prede-
termined moisture status in the plant root zone.

Price ranges of controllers will vary widely with
the complexity of the device. However, for most
home systems controllers will range from $50 -
$200.

Backflow prevention
Irrigation systems which use municipal water
supplies and irrigation systems in which chemicals
are injected require backflow prevention systems.
The specifications for backflow prevention systems
are given by state law, a city ordinance, or other
codes. It is important to make sure that the system
is in agreement with the backflow prevention re--
quirements of the local municipality. Generally, a
reduced pressure principle device is required if
chemicals are injected into the irrigation system
and the water supply is municipal water. For
irrigation wells, a combination of check valve, low


11









pressure drain, and a vacuum breaker may be suffi-
cient A detailed description of these requirements
can be found in IFAS Extension Bulletin 217,
Backflow Prevention Requirements For Florida Irri-
gation Systems and IFAS Extension Bulletin 248,
Backflow Prevention Requirements For Irrigation
Systems Using Municipal Water Supplies.

Some rules of good design
Good sprinkler systems should water the area
completely, uniformly, and in accordance with the
wishes of the owner. A comprehensive plan of the
area to exact scale is necessary. The first step is to
decide on the type of sprinkler heads to be used.
The system should be designed for complete cover-
age. Sprinklers should be selected on the basis of
the type of area to be covered (ground cover,
shrubs, lawn), the water flow rate and pressure
available, soil infiltration characteristics, and the
scope of the area to be covered. The sprinklers
must be fitted to the area and carefully placed
within the maximum recommended spacing (this is
usually 50-60% of the diameter of coverage). If it is
possible, triangular spacing of sprinklers should be
selected over rectangular since it provides better
coverage. Full circle and part circle coverage pat-
terns also should be selected where appropriate. In
many residential areas there is not enough space to
establish a typical rectangular or triangular pat-
tern for sprinklers. In such cases it is best to select
the sprinklers for the bordered areas such as build-
ings, sidewalks, walls and patios first and then fill
the middle areas with sprinklers so that uniformity
of application will be sufficient.

For micro-irrigation systems it is important to
provide required lower pressure by using appropri-
ate pressure regulators. It is important to make
sure that the spacing of the emitters will provide
sufficient distribution of water in the lateral direc-
tion resulting in uniform water application. For
more information a reader should consult IFAS
publication AE-24, Principles of Micro-Irrigation.

Refinement of the system
An irrigation system should be designed with
separate zones for different vegetation with differ-
ent water requirements or different root depths.
For example, flower beds should be watered sepa-
rately from lawn areas. This requires additional
pipe, fittings, sprinkler heads, and valves. This
type of refinement for watering will increase the
initial cost of the system, but it will often result in
a savings of water and the possibility of supplying
different amounts of water for different plants.


It is important to keep in mind that for unifor-
mity reasons, sprinklers with different application
rates and different watering patterns should be
placed in separate zones. If full-circle sprinklers
are in the same zone with half-circle sprinklers, the
nozzles for the half-circle sprinklers should be se-
lected so that the flow rate is half of the flow rate
from the full-circle sprinklers. In addition, spray
heads, rotary sprinklers, and micro-systems should
be installed in separate zones since they usually
have different pressure requirements, different ap-
plication rates, and different required times of op-
eration.

Root zone characteristics vary from turf to
shrubs to trees. Therefore, it may be necessary to
place zones according to plants with similar root
zones to avoid over- or under-irrigation of dissimi-
lar plants within the same zone.


Importance of sprinkler
overlapping

Most sprinklers have a decreasing application
rate from the sprinkler head out to the maximum
diameter of throw (Figure 11a). This occurs be-
cause the area to be covered increases as distance
from the sprinkler increases. Because of this pat-
tern it is necessary that sprinklers overlap in order
to achieve a uniform application. Usually there is a
plateau in the sprinkler distribution pattern before
the descent begins. Generally, the larger this pla-
teau, the further apart sprinklers can be placed.
However, a safe rule of thumb is to make sure
that the last droplets of one sprinkler reach the ad-
jacent sprinkler. This is a 50% overlap of wetting
patterns.

Quite often a typical distribution curve for a par-
ticular sprinkler is supplied by the sprinkler manu-
facturer. To measure the distribution pattern,
collect water along the radius of the pattern in



ao'- A

.oi"-


FEAD FEET MAXIMUM
LOCATION DIAMETER
LOCAFigure 11. Typical distribution curve for a sprinkler head.


12









pressure drain, and a vacuum breaker may be suffi-
cient A detailed description of these requirements
can be found in IFAS Extension Bulletin 217,
Backflow Prevention Requirements For Florida Irri-
gation Systems and IFAS Extension Bulletin 248,
Backflow Prevention Requirements For Irrigation
Systems Using Municipal Water Supplies.

Some rules of good design
Good sprinkler systems should water the area
completely, uniformly, and in accordance with the
wishes of the owner. A comprehensive plan of the
area to exact scale is necessary. The first step is to
decide on the type of sprinkler heads to be used.
The system should be designed for complete cover-
age. Sprinklers should be selected on the basis of
the type of area to be covered (ground cover,
shrubs, lawn), the water flow rate and pressure
available, soil infiltration characteristics, and the
scope of the area to be covered. The sprinklers
must be fitted to the area and carefully placed
within the maximum recommended spacing (this is
usually 50-60% of the diameter of coverage). If it is
possible, triangular spacing of sprinklers should be
selected over rectangular since it provides better
coverage. Full circle and part circle coverage pat-
terns also should be selected where appropriate. In
many residential areas there is not enough space to
establish a typical rectangular or triangular pat-
tern for sprinklers. In such cases it is best to select
the sprinklers for the bordered areas such as build-
ings, sidewalks, walls and patios first and then fill
the middle areas with sprinklers so that uniformity
of application will be sufficient.

For micro-irrigation systems it is important to
provide required lower pressure by using appropri-
ate pressure regulators. It is important to make
sure that the spacing of the emitters will provide
sufficient distribution of water in the lateral direc-
tion resulting in uniform water application. For
more information a reader should consult IFAS
publication AE-24, Principles of Micro-Irrigation.

Refinement of the system
An irrigation system should be designed with
separate zones for different vegetation with differ-
ent water requirements or different root depths.
For example, flower beds should be watered sepa-
rately from lawn areas. This requires additional
pipe, fittings, sprinkler heads, and valves. This
type of refinement for watering will increase the
initial cost of the system, but it will often result in
a savings of water and the possibility of supplying
different amounts of water for different plants.


It is important to keep in mind that for unifor-
mity reasons, sprinklers with different application
rates and different watering patterns should be
placed in separate zones. If full-circle sprinklers
are in the same zone with half-circle sprinklers, the
nozzles for the half-circle sprinklers should be se-
lected so that the flow rate is half of the flow rate
from the full-circle sprinklers. In addition, spray
heads, rotary sprinklers, and micro-systems should
be installed in separate zones since they usually
have different pressure requirements, different ap-
plication rates, and different required times of op-
eration.

Root zone characteristics vary from turf to
shrubs to trees. Therefore, it may be necessary to
place zones according to plants with similar root
zones to avoid over- or under-irrigation of dissimi-
lar plants within the same zone.


Importance of sprinkler
overlapping

Most sprinklers have a decreasing application
rate from the sprinkler head out to the maximum
diameter of throw (Figure 11a). This occurs be-
cause the area to be covered increases as distance
from the sprinkler increases. Because of this pat-
tern it is necessary that sprinklers overlap in order
to achieve a uniform application. Usually there is a
plateau in the sprinkler distribution pattern before
the descent begins. Generally, the larger this pla-
teau, the further apart sprinklers can be placed.
However, a safe rule of thumb is to make sure
that the last droplets of one sprinkler reach the ad-
jacent sprinkler. This is a 50% overlap of wetting
patterns.

Quite often a typical distribution curve for a par-
ticular sprinkler is supplied by the sprinkler manu-
facturer. To measure the distribution pattern,
collect water along the radius of the pattern in



ao'- A

.oi"-


FEAD FEET MAXIMUM
LOCATION DIAMETER
LOCAFigure 11. Typical distribution curve for a sprinkler head.


12









pressure drain, and a vacuum breaker may be suffi-
cient A detailed description of these requirements
can be found in IFAS Extension Bulletin 217,
Backflow Prevention Requirements For Florida Irri-
gation Systems and IFAS Extension Bulletin 248,
Backflow Prevention Requirements For Irrigation
Systems Using Municipal Water Supplies.

Some rules of good design
Good sprinkler systems should water the area
completely, uniformly, and in accordance with the
wishes of the owner. A comprehensive plan of the
area to exact scale is necessary. The first step is to
decide on the type of sprinkler heads to be used.
The system should be designed for complete cover-
age. Sprinklers should be selected on the basis of
the type of area to be covered (ground cover,
shrubs, lawn), the water flow rate and pressure
available, soil infiltration characteristics, and the
scope of the area to be covered. The sprinklers
must be fitted to the area and carefully placed
within the maximum recommended spacing (this is
usually 50-60% of the diameter of coverage). If it is
possible, triangular spacing of sprinklers should be
selected over rectangular since it provides better
coverage. Full circle and part circle coverage pat-
terns also should be selected where appropriate. In
many residential areas there is not enough space to
establish a typical rectangular or triangular pat-
tern for sprinklers. In such cases it is best to select
the sprinklers for the bordered areas such as build-
ings, sidewalks, walls and patios first and then fill
the middle areas with sprinklers so that uniformity
of application will be sufficient.

For micro-irrigation systems it is important to
provide required lower pressure by using appropri-
ate pressure regulators. It is important to make
sure that the spacing of the emitters will provide
sufficient distribution of water in the lateral direc-
tion resulting in uniform water application. For
more information a reader should consult IFAS
publication AE-24, Principles of Micro-Irrigation.

Refinement of the system
An irrigation system should be designed with
separate zones for different vegetation with differ-
ent water requirements or different root depths.
For example, flower beds should be watered sepa-
rately from lawn areas. This requires additional
pipe, fittings, sprinkler heads, and valves. This
type of refinement for watering will increase the
initial cost of the system, but it will often result in
a savings of water and the possibility of supplying
different amounts of water for different plants.


It is important to keep in mind that for unifor-
mity reasons, sprinklers with different application
rates and different watering patterns should be
placed in separate zones. If full-circle sprinklers
are in the same zone with half-circle sprinklers, the
nozzles for the half-circle sprinklers should be se-
lected so that the flow rate is half of the flow rate
from the full-circle sprinklers. In addition, spray
heads, rotary sprinklers, and micro-systems should
be installed in separate zones since they usually
have different pressure requirements, different ap-
plication rates, and different required times of op-
eration.

Root zone characteristics vary from turf to
shrubs to trees. Therefore, it may be necessary to
place zones according to plants with similar root
zones to avoid over- or under-irrigation of dissimi-
lar plants within the same zone.


Importance of sprinkler
overlapping

Most sprinklers have a decreasing application
rate from the sprinkler head out to the maximum
diameter of throw (Figure 11a). This occurs be-
cause the area to be covered increases as distance
from the sprinkler increases. Because of this pat-
tern it is necessary that sprinklers overlap in order
to achieve a uniform application. Usually there is a
plateau in the sprinkler distribution pattern before
the descent begins. Generally, the larger this pla-
teau, the further apart sprinklers can be placed.
However, a safe rule of thumb is to make sure
that the last droplets of one sprinkler reach the ad-
jacent sprinkler. This is a 50% overlap of wetting
patterns.

Quite often a typical distribution curve for a par-
ticular sprinkler is supplied by the sprinkler manu-
facturer. To measure the distribution pattern,
collect water along the radius of the pattern in



ao'- A

.oi"-


FEAD FEET MAXIMUM
LOCATION DIAMETER
LOCAFigure 11. Typical distribution curve for a sprinkler head.


12









several locations (Figure 11b) and the application
depths can be easily determined. By using a stop-
watch and measuring the time required to apply a
certain depth, application rates can be determined
as well. This will help in management of the sys-
tem. Proper overlapping of the sprinklers will
provide increased uniformity in water distribution
(Figure llc) over irrigated areas. Poor uniformity
will result in some areas being over-irrigated and
some areas being under-irrigated, which could
result in plant stress.


Figure 11b. Determination of sprinkler distribution pattern
using catch cans.


LL
z
a.


CUMULATIVE
(APPLICATION


40,
.35.
30,
.25-
.20,
.15-
.10.
.05-


I T IV 0 O 2 5 30 W0 40 43
SPRINKLER FEET
LOCATION
Figure tic. Effect of sprinkler overlapping.


SPRWKLER
LOCATION


System management
Irrigation management involves maintenance of
the system, as well as scheduling irrigations.
Maintenance involves cleaning, repairing, and
replacing components as necessary to maintain an
efficient and properly operating system. Sprinkler
systems generally require less maintenance than
micro-irrigation systems. Periodic visual inspection
of sprinkler heads and their operation is usually
sufficient. Once a year the nozzles may be checked
with an appropriately sized drill bit for change in
size due the wear or clogging. Micro-irrigation
requires more maintenance. More details on
micro-irrigation maintenance are given in IFAS


Bulletin 245, Micro-Irrigation on Mulched Bed
Systems: Components, System Capacities and
Management. In addition to routine maintenance,
the system should be checked for clogging and
uniformity of water application. The procedure is
described in IFAS Bulletin 195 Field Evaluation of
Trickle Irrigation Systems: Uniformity of Water
Application.

Irrigation scheduling involves a decision-making
process of when to irrigate and how much to apply
or how long the system should be operated. The
scheduler must decide on the objective of the irriga-
tion and the type of information required to accom-
plish scheduling. Objectives may involve drought
stress avoidance, frost protection, or crop cooling.
This publication discusses only drought stress
'avoidance. The decision process can be influenced
by several factors and requires careful examination
of the available information.

Scheduling to avoid drought
stress
Drought stress can be controlled by irrigation.
Scheduling the time and amount of application will
depend on the availability of water as well as the
soil water status, allowable depletion, and water
use rate. Table 2 provides monthly potential
evapotranspiration (ETp) levels for north and south
Florida during each month. Figure 12 shows the
division of Florida into two regions (North and
South). For turf, the actual evapotranspiration
rate is near the value of ETp, and Table 2 can be
used to approximate turf water requirements. For
other plants, the actual ET rate will vary, but it is
directly related to ETp. In this case, ETp must be

M r O NORTH REGION

















Figure 12. North and south evapotranspiration regions of
Florida.


13









several locations (Figure 11b) and the application
depths can be easily determined. By using a stop-
watch and measuring the time required to apply a
certain depth, application rates can be determined
as well. This will help in management of the sys-
tem. Proper overlapping of the sprinklers will
provide increased uniformity in water distribution
(Figure llc) over irrigated areas. Poor uniformity
will result in some areas being over-irrigated and
some areas being under-irrigated, which could
result in plant stress.


Figure 11b. Determination of sprinkler distribution pattern
using catch cans.


LL
z
a.


CUMULATIVE
(APPLICATION


40,
.35.
30,
.25-
.20,
.15-
.10.
.05-


I T IV 0 O 2 5 30 W0 40 43
SPRINKLER FEET
LOCATION
Figure tic. Effect of sprinkler overlapping.


SPRWKLER
LOCATION


System management
Irrigation management involves maintenance of
the system, as well as scheduling irrigations.
Maintenance involves cleaning, repairing, and
replacing components as necessary to maintain an
efficient and properly operating system. Sprinkler
systems generally require less maintenance than
micro-irrigation systems. Periodic visual inspection
of sprinkler heads and their operation is usually
sufficient. Once a year the nozzles may be checked
with an appropriately sized drill bit for change in
size due the wear or clogging. Micro-irrigation
requires more maintenance. More details on
micro-irrigation maintenance are given in IFAS


Bulletin 245, Micro-Irrigation on Mulched Bed
Systems: Components, System Capacities and
Management. In addition to routine maintenance,
the system should be checked for clogging and
uniformity of water application. The procedure is
described in IFAS Bulletin 195 Field Evaluation of
Trickle Irrigation Systems: Uniformity of Water
Application.

Irrigation scheduling involves a decision-making
process of when to irrigate and how much to apply
or how long the system should be operated. The
scheduler must decide on the objective of the irriga-
tion and the type of information required to accom-
plish scheduling. Objectives may involve drought
stress avoidance, frost protection, or crop cooling.
This publication discusses only drought stress
'avoidance. The decision process can be influenced
by several factors and requires careful examination
of the available information.

Scheduling to avoid drought
stress
Drought stress can be controlled by irrigation.
Scheduling the time and amount of application will
depend on the availability of water as well as the
soil water status, allowable depletion, and water
use rate. Table 2 provides monthly potential
evapotranspiration (ETp) levels for north and south
Florida during each month. Figure 12 shows the
division of Florida into two regions (North and
South). For turf, the actual evapotranspiration
rate is near the value of ETp, and Table 2 can be
used to approximate turf water requirements. For
other plants, the actual ET rate will vary, but it is
directly related to ETp. In this case, ETp must be

M r O NORTH REGION

















Figure 12. North and south evapotranspiration regions of
Florida.


13









multiplied by a crop coefficient for a given plant
and growth stage. Thus, Table 2 cannot be used
directly.

Table 2. Potential evapotranspiration (ETp) levels for two re-
gions of Florida, north and south (Figure 12).
North region South region
Month ETp (inlday) ETp (inJday)

1 0.07 0.09
2 0.10 0.12
3 0.13 0.15
4 0.17 0.19
5 0.19 0.20
6 0.19 0.19
7 0.18 0.19
8 0.17 0.17
9 0.15 0.16
10 0.12 0.14
11 0.09 0.11
12 0.06 0.09


Soil water status
Moisture available to the plant is influenced by
the available water holding capacity (AWHC) of the
soil. The AWHC is defined as the amount of water
that can be held by the soil between the permanent
wilting point and field capacity of the soil. Perma-
nent wilting point is the soil water content where
the plant is no longer able to extract water. Field
capacity refers to the water content of the soil after
it has been fully wetted, and excess water has
drained.

Additional soil information necessary to the irri-
gation scheduler includes the available water in the
soil at the time of irrigation. The available water is
that amount of water contained in the soil at the
time of interest within the AWHC range. This
property may be monitored with soil water sensors.
One type of sensor, called a tensiometer is very ap-
plicable to sandy soils. Additional information can
be obtained from IFAS Circulars 487, Tensiometers
for Soil Moisture Measurement and Irrigation
Scheduling, and 532, Measurement of Soil Water
For Irrigation Management.

The soil water properties are dependent upon
the soil type and texture. Sandy soils have low wa-
ter-holding capacities (0.5 to 1.0 inches of water per
foot depth of soil) as compared to the water-holding
capacities of loam or clay soils (2.0 to 3.0 inches of
water per foot depth of soil). Therefore, more fre-
quent, smaller amounts of irrigation are required


on a sandy soil to avoid movement of water below
the plant root zone. For example, if a soil has an
AWHC of 1-inch of water per foot depth of soil, and
a plant root zone is limited to a 1-foot root depth,
the maximum depth of water that can be held in
this root zone is 1-inch. If irrigation exceeds this
amount, the additional water will percolate down-
ward out of the root zone and will be unavailable to
the plant.

Allowable depletion
The allowable depletion is the level of water
depletion which will be allowed before irrigation
will be applied. The level of allowable depletion
will vary with the plant characteristics as well as
the irrigation system characteristics and capacities.

Plants sensitive to water stress may be irrigated
at 20 to 30 percent depletion levels (80 to 70
percent of available water remaining in the soil).
However, most plants will be irrigated in the 40 to
60 percent depletion range.

Irrigation system design may be such that the
time required to complete the cycle of irrigation for
all zones will not allow the irrigation of the same
zone before 50% depletion occurs. If drought sensi-
tive plants are being grown and the irrigation is
designed at 30% depletion this system will not be
sufficient. An irrigation system with a larger
capacity is required for these plants.

Water use rate
The plant water use rate may be obtained
directly or estimated. However, it is very difficult
to obtain direct information, and therefore, most
water use data are estimated. Estimation methods
can involve the use of field sensors, measured pan
evaporation data, published data, or broadcast
information.

Scheduling by the accounting
method
After compilation of soil, plant, and climatic
data, the irrigation scheduler must design a pro-
gram which meets the needs of the plants. One
type of scheduling program utilizes an accounting
procedure (see IFAS Circular 431, Irrigate by the
Accounting Method) to record inputs and outputs of
water to and from the irrigated area.

Example: A homeowner located in Orlando has a
lawn irrigated with a sprinkler system. The system
delivers water at a rate of 0.5 inches per hour. The


14









lawn has an 12-inch root zone and is on a sandy soil
with an available water holding capacity of 0.9
inches of water per foot depth of soil. It is April
and the turf requires 0.15 inches of water per day
to meet the environmental demand for water.
What type of scheduling program will meet the
needs of this situation?

1. Establish a level of allowable depletion, say
50%.

2. Determine the available water holding capacity
of the root zone:


12-in.
root
zone


0.9 in. water 1-ft.
ft. of soil 12-in.
ft. of soil 12-in.


= 0.9 in. of
available water


3. Number of days between irrigations:

0.9 inches 0.50 depletion
available level
= 3 days between
0.15 inches of demand per day irrigations

Irrigation depths of 0.45 inches will then be ap-
plied every 3 days if rainfall does not occur. How-
ever, no irrigation system is 100% efficient, due to
wind, evaporation and runoff. Assuming an effi-
ciency of 75%, the irrigation depth applied must be
0.60 (0.45/0.75) inches in order to deliver .45 inches
of water to the root zone. Water amounts greater
than this will move out of the root zone and will be
unavailable to the plant. If the profile is allowed to
fully deplete, 1.2 inches of water should be applied
every 6 days. However, this would result in plant
stress and is not recommended.

4. Operation time:

[0.60 inches to apply]
= 1.2 hours (72 minutes)
[0.5 inches per hour]

As a final note, if the homeowner could only irri-
gate one day a week, then 7 (0.15 inches/.75) = 1.4
inches of water must be applied at once to provide
water for the entire week. However, part of the wa-
ter will be wasted. Applying 1.4 inches of water de-
livers 1.05 inches (weekly requirement) to the soil
due to an application efficiency of 60%. Therefore,
since this soil can hold only 0.9 inches of available
water in the root zone, 0.15 inches of water will be
wasted.


References
Augustine, B.J. 1987. Let Your Lawn Tell You
When To Water. Florida Cooperative Ext. Service,
IFAS, University of Florida, Gainesville, FL 32611.
Fact Sheet OH 63.

Augustine, B. J. 1987. Preparing Your Lawn
For Drought. Florida Cooperative Ext. Service,
IFAS, University of Florida, Gainesville, FL 32611.
Fact Sheet OH-57.

Choate, R. E. and D. S. Harrison. 1988. Irrigate
By the Accounting Method. Florida Cooperative
Ext. Service, IFAS, University of Florida,
Gainesville, FL 32611. Circular 431.

Clark, G. A., C. D. Stanley and A. G. Smajstrla.
1988. Micro-Irrigation on Mulched Bed Systems:
Components, System Capacities and Management.
Florida Cooperative Ext. Service, IFAS, University
of Florida, Gainesville, FL 32611. Bulletin 245.

Haman, D. Z. and F. T. Izuno. 1987. Principle of
Micro-Irrigation. Florida Cooperative Ext. Service,
IFAS, University of Florida, Gainesville, FL 32611.
Fact Sheet AE-24.

Haman, D. Z., A. G. Smajstrla and F. S. Zazueta.
1986. Screen Filters in Trickle Irrigation Systems.
Florida Cooperative Ext. Service, IFAS, University
of Florida, Gainesville, FL 32611. Fact Sheet AE-
61.

Pair, C. H., W. H. Hinz, K R. Frost, R. E. Sneed
and T. J. Schiltz. 1983. Irrigation. Fifth edition.
The Irrigation Association. Silver Spring, MD.

Sarsfield, A. C. 1966. The ABC's of Lawn
Sprinkler Systems. Irrigation Technical Services
Publication Division, P. O. Box 268, Lafayette, CA
94549.

Smajstrla, A. G. 1988. Backflow Prevention Re-
quirements For Irrigation Systems Using Municipal
Water Supplies. Florida Cooperative Ext. Service,
IFAS, University of Florida, Gainesville, FL 32611.
Bulletin 248.

Smajstrla, A. G. and D. S. Harrison. 1988.
Measurement of Soil Water For Irrigation Manage-
ment. Florida Cooperative Ext. Service, IFAS,
University of Florida, Gainesville, FL 32611.
Circular 532.


15









Smajstrla, A. G., D. S. Harrison, and F. X
Duran. 1987. Tensiometers for Soil Moisture
Measurement and Irrigation Scheduling. Florida
Cooperative Ext. Service, IFAS, University of
Florida, Gainesville, FL 32611. Circular 487.

Smajstrla, A. G., D. S. Harrison and G. A. Clark.
1985. Trickle Irrigation Scheduling I: Durations of
Water Applications. Florida Cooperative Ext.
Service, IFAS, University of Florida, Gainesville,
FL 32611. Bulletin 204.


Smajstrla A. G., D. S. Harrison and F. S.
Zazueta. 1985. Field Evaluation of Trickle Irriga-
tion Systems: Uniformity of Water Application.
Florida Cooperative Ext. Service, IFAS, University
of Florida, Gainesville, FL 32611. Bulletin 195.

Smajstrla, A. G., D. S. Harrison, W. J. Becker,
F. S. Zazueta and D. Z. Haman. 1985. Backflow
Prevention Requirements for Florida Irrigation
Systems. Florida Cooperative Ext. Service, IFAS,
University of Florida, Gainesville, FL 32611.
Bulletin 217.


COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,JohnT.Woeste,
Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth
publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state purchasers
is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida32611. Before publicizing
this publication, editors should contact this address to determine availability. Printed 1/92.




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