Measuring Water Levels In Wells: An Inexpensive Electric Water Level Indicator

http://edis.ifas.ufl.edu/ ( Publisher's URL )
MISSING IMAGE

Material Information

Title:
Measuring Water Levels In Wells: An Inexpensive Electric Water Level Indicator
Physical Description:
Fact sheet
Creator:
Hood, C.F.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

Notes

Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"Publication date: November 1991."
General Note:
"EES-62"

Record Information

Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004812:00001


This item is only available as the following downloads:


Full Text

PAGE 1

FactSheetEES-62 November1991 MeasuringWaterLevelsinWells: AnInexpensiveElectricWaterLevelIndicator1 C.F.Hood,A.G.Smajstria,andF.S.Zazueta2Itisoftennecessarytomeasurethedepthto waterinawell.Thedepthtowaterinfluencespump selectionandplacement.Italsodeterminesthe energyrequiredtoliftwatertothesurfaceinthe pumpingprocessandthusaffectsthehorsepower requirementsofthepumpingsystem.Itmustalsobe measuredtoevaluatetheefficiencyofirrigation pumpingsystemstodeterminetheneedforpump repairorreplacement. Whenapumpdischargeswaterfromawell,the waterlevelinthewelldrops.Thisoccursbecause frictionlossespreventinstantaneouswaterflowfrom theaquifertothewelltoreplacethatwhichthepump hasdisplaced.Thisdropinwaterlevelinthewell duringpumpingiscalled drawdown. Drawdownincreasesthedepthtothewater surfaceinawell.Becauseofdrawdown,morework mustbedonetoliftwatertothesurface,andthus moreenergyisusedinpumping.Becausedrawdown changesthewaterlevelinawell,thepumpingwater levelisthewaterlevelwhichmostinfluencespump selection,placement,andpowerrequirements. Drawdownisnotaconstant,evenforagiven geographicallocation.Rather,drawdowndepends uponthewellsize,rateofpumping,aquifer Figure1.Detailsoftheelectricwaterlevelindicator. characteristics,andtypeandqualityofwell construction.Therefore,ifpumpingwaterlevelsare tobeaccuratelyknown,theymustbemeasuredfor eachwellandpumpingconditions. 1.ThisdocumentisFactSheetEES-62,aseriesoftheFloridaEnergyExtensionService,FloridaCooperativeExtensionService,InstituteofFood andAgriculturalSciences,UniversityofFlorida.Publicationdate:November1991. 2.C.F.Hood,EnergyExtensionSpecialist,AgriculturalEngineeringDept.;A.G.Smajstrla,Professor,AgriculturalEngineeringDept.;F.S. Zazueta,AssociateProfessor,AgriculturalEngineeringDept.,CooperativeExtensionService,InstituteofFoodandAgriculturalSciences, UniversityofFlorida,GainesvilleFL32611. TheFloridaEnergyExtensionServicereceivesfundingfromtheFloridaEnergyOffice,DepartmentofCommunityAffairsandisoperated bytheUniversityofFlorida'sInstituteofFoodandAgriculturalSciencesthroughtheCooperativeExtensionService.Theinformation containedhereinistheproductoftheFloridaEnergyExtensionServiceanddoesnotnecessarilyreflecttheviewsoftheFloridaEnergyOffice. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

PAGE 2

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page2Thisfactsheetpresentsthedetailsfor constructionanduseofaninexpensiveelectricwater levelindicator.Thisinstrumentcostsapproximately $25toconstruct,yetitcanbeusedtomeasurewater levelsinawellwithsufficientaccuracyforthe purposespreviouslymentionedbothbeforeand duringpumping.Italsoisportableandeasytouse. Thisinstrumentcouldbeusedby(1)irrigation managerstomeasurepumpingwaterlevelsforpump performancetesting,(2)welldrillerstodetermine depthstowatertablesandforwellperformancetests, (3)pumpinstallersandconsultantstodeterminethe properplacementandselectionofpumps,andto "troubleshoot"systemsinneedofrepair,and(4)U.S. GeologicSurvey,WaterManagementDistrict,and otherpersonneltoevaluateaquifercharacteristics.DETAILSOFCONSTRUCTIONTheelectricwaterlevelindicatorshowninFigure 1canbeconstructedusingmaterialsavailableatlocal electronicssuppliers.Acompletelistingof componentsisgiveninTable1.Thetotalcostofthe componentswaslessthan$25whenthisfactsheet waspublished.ReelUnitAmajorcomponentofthewaterlevelindicator isthereelofwire.Aspoolofapproximately22 gaugeaudiohookupwireissuitableforthispurpose. However,anysmall-gaugestrandedinsulatedwirecan alsobeused.Thewiremustbelongenoughtoreach thegreatestanticipatedwaterdepth.Strandedrather thansolidwireshouldbeusedbecauseflexibilityis necessarywhenthewireisloweredintothesmall spacebetweenthewellcasingandcolumnpipe. ThereelshowninFigure1maybeconstructed usingsmalldiametermetalrod(threaded)for handles,andusingthespoolpurchasedwiththewire. Forconvenience,apermanentmarkingpencanbe usedtomarkthewireinfive-footincrements. Alternatively,ateachmeasurementthewirecanbe extractedfromthewell,laidoutontheground,and thenmeasuredtodeterminethedepthtothewater table. Thewaterlevelindicatoroperateswhenan electriccircuitiscompletedbythetwobareendsof thesoundingwirescontactingthewatersurfaceinthe well.Therefore,thosewiresshouldbestrippedfora shortlengthtoallowreadyaccesstothewater.Lead fishingweightscanbeattachedtooneofthebare Table1.ElectricWaterLevelIndicatorPartsList 1-Spoolonwhichtowindsoundingwireandmount thecircuit. 1-Wire-2conductor,insulated,lightgauge(~22 ga),stranded,about100to300feetlong dependingonwaterdepthtobemeasured. 1-2N3904NPNtransistor,orequivalent. 1-100-ohmresistor,1/2watt. 1-1k(1000)-ohmresistor,1/2watt. 1-10k(10,000)-ohmresistor,1/4or1/2watt. 1-High-BrightnessLightEmittingDiode(LED)(Cat. No.276-066A*). 1-Buzzer(optional)(Cat.No.273-065). 1-SinglePole-SingleThrow(SPST)switch(Cat.No. 275-612). 1-Battery,9-Volt. 1-9-VoltBatteryClip(Cat.No.270-325). 1-9-VoltBatteryHOlder(Cat.No.270-326). 1-Experimenter'sBoxwithPCBoard(Cat.No.270283). 1-Tubeofsiliconesealant. -Hardwaretomakehandles. -Leadfishingweights. *CatalognumbersareforArcherbrand(Radio Shack)parts.Tradenamesofproducts,where given,areusedforthepurposeofproviding specificinformation.Useofacommercialname isnotintendedasanendorsementofproducts named,norascriticismofsimilarproductsnot named.wirestoallowthewiretobelowereddirectlytothe watertable.Smalldiameterweightsshouldbeused toavoidlodgingtheminthewell.However,a sufficientnumberofweightsmustbeusedtopullthe flexiblesoundingwiredownintothewellandto ensurethatthewireisstraightwhenmeasurements aremade. Leadweightsshouldbeusedbecausetheyare relativelysoftandcanoftenbepulledfreeifthey becomelodgedbetweenthecasingandpump dischargepipe.Also,ifweightscomelooseanddrop

PAGE 3

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page3intothewell,theywillfalltothebottomandwillnot Figure2.Electroniccircuit. interferewiththepumpingoperations.ElectronicCircuitryThecircuitdescribedinthispublicationdetects immersionofthebareendsofthesoundingwireby takingadvantageofthefactthatwaterwillconduct electricitybetterthanair.Whenthebareendsofthe wirebothtouchthewater,currentwillbegintoflow; however,insufficientcurrentwillflowtodirectly causeaLEDtogloworabuzzertosound.A transistorhasbeenaddedtoamplifythissmall currenttothelevelnecessaryfortheLEDand/or buzzertooperateproperly.Althoughtherearemany possiblewaystoamplifythecurrentflowingthrough theleads,thecircuitshownherewaschosenasthe simplest

PAGE 4

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page4alternativecapableofreliablyindicatingwaterlevel. Inordertomaintainsimplicity,noattempthasbeen madetoprotectthecircuitfromsomeinfrequent,but potentiallydamaging,events.Themostnotableof theseomissionsare: 1.Thecircuitprovidesnoprotectionfromstatic discharge.Walkingacrossacarpetedfloorthen dischargingasparkintotheendsofthesounding wirewillverylikelydestroythetransistor.Static dischargeisrarelyaprobleminthefield;when workingonthedeviceindoors,merelytoucha metallicsurfacetodrainanystaticbuildupfrom yourbodybeforeworkingonthecircuit. 2.A9-volt"transistor"batteryandpolarizedsnap-on batteryleadshavebeenspecifiedtoinsureproper voltageandpolarityforthiscircuit.Additional protectivemeasureshavenotbeenincludedinthe designtoavoiddamagecausedbyreversed polarityorexcessivevoltagesfrom"jury-rigged" powersources. 3.Thecircuithasnotbeendesignedtopreclude electrolysisattheendofsoundingwiredueto prolongedsubmersion.Thecircuitshowninthis FactSheetisdesignedforintermittentuseitis notsuitableforcontinuouswaterleveldetection (suchasinasump).Continuousoperationofthe devicewiththeleadssubmergedwillresultin failuretodetectthewaterafterafewdays operation. Theelectroniccircuitrecommendedtodetect immersionofthebareendsofthesoundingwireis showninFigure2(A,B,C,D).Thisdesignincludes bothanLEDandabuzzertoindicatecontactwith thewater.Thecircuitwilloperateproperlywith eitheromitted.Figure2aisthecircuitschematic,2b isthepinoutofthetransistorandLEDusedinthe circuit,2cisapictorialrepresentationoftheproper waytoassemblethecircuitiftheexperimenter's circuitboxisused,2distheholepatternforthecover includedwiththeexperimenter'sbox,and3isa photographofanassembledunit.CircuitConstructionConstructthecircuitonthecircuitboardprovided withtheexperimenter'sboxidentifiedinthepartslist or,alternatively,onapieceofbareperforatedcircuit board.Theboardprovidesamountingsurfaceand ensuresmechanicalstabilityofthecomponents.Short Figure3.Sketchofassembly. lengthsofinsulatedcopperwirecanbeusedonthe bottomoftheboardtoprovideconnectionsbetween thevariouscomponents. Allcomponentsmustbesolderedtoensuregood connections(useonlyrosincoresolder).The preferredsolderinginstrumentisa15-25-wattpenciltypesolderingiron.Whensoldering,beverycareful toavoidexcessiveheatingoftheLEDandtransistor: aheatsinkshouldbeusedbetweentheelectronic componentsandthepointofsolderingtoavoid overheating.Heatsinkingcanbeaccomplishedby grippingthecomponentleadbetweenthecomponent bodyandthesolderingpointwithasmallpairof needlenosepliersorbyattachingasmallalligatorclip closetothecomponentbody. TheproperorientationoftheLED,transistor, andbatteryarecriticaltotheproperoperationofthe circuit;however,theleadsontheresistors,switch, andsoundingwirecanbereversedwithoutaffecting thecircuitoperation.Thebuzzermayormaynot requireaspecificorientation.RefertoFigure2band theparagraphsbelowtodetermineproper orientation. LED: NoteinFigure2dthattheLEDhasone flattenedsideatthebase.Thelegadjacenttotheflat sideisthecathodeornegativeleadoftheLED. Connectthenegative(cathode)leadtothe100-ohm, 1/2-wattresistorasshowninFigure2a&c,andthe positive(anode)leadtothebatterypositiveleadat pointB.(Assemblyhint:raisetheLED approximately0.15inchfromthecircuitboard surfacethiswillfacilitateheatsinkingduring solderingandwillmadetheLEDmorevisibleby

PAGE 5

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page5causingittoprotrudethroughtheboxcover.)Donot touchtheleadsoftheLEDdirectlytothebattery terminaltodeterminepolarity:afresh9-voltbattery willalmostcertainlydestroytheLED. Transistor: The2N3904transistorcantake severalformsdependingonthepackagestyle(Figure 2b).Plasticencapsulatedtransistorsareusuallythe leastexpensivedevicesandwillprobablyhavepinouts asshownineitherthecenterorrighthanddrawing. Metalencapsulatedtransistorswillhavepinoutsas shownontheleft.Notethatthesedrawingsshowthe bottomofthetransistor.Becarefultoconnectthe Base,collector,andEmitterleadsasshowninFigure 2a&c.(Assemblyhint:layplastictransistorflaton itsbacktoprovideclearancefortheboxcover.) Battery/batteryleads: Thesnap-onleadsforthe9voltbatteryarepolarizedsuchthattheredleadis connectedtothepositiveterminal.Connectthered leadtooneterminaloftheswitchandtheblacklead topointGofthecircuit. Buzzer: Asindicatedabove,thebuzzermayor maynotbepolarized.Studythepackagingcarefully andlookforanymentionofproperorientation.If thepackagingmakesnomentionofpolarity,lookat thebottomofthebuzzer:somewillhavepolarity markedwith"+"and"-"(thebuzzergivenintheparts listismarkedinthismanner).Connectthepositive ("+")leadtopointBofthecircuit.Ifpolarityisnot indicatedandthereisoneredwire,connectitto pointB.Buzzersareoftenspecifiedasoperableover aparticularvoltagerange,e.g.,3-18volts,withlouder soundoccurringatthehighendoftheoperating voltage.Purchaseonewithanoperatingrange bracketing9voltswiththehighendascloseto9volts aspossible.Donotuseabuzzerwithanuppervoltagespecificationlessthan9volts,becauseitmay bedamagedinthiscircuit.TestingtheWaterlevelIndicatorThewaterlevelindicatormayeasilybetested beforeusingitinthefieldbydippingthebareendsof thesoundingwiresintowaterandobservingthelight emittingdiode(LED)andlisteningforthebuzzerto sound.TheLEDshouldlightandthebuzzershould soundwhenthebareendsofthewirecontactthe water.Alternatively,theunitcanbetestedby touchingthebareendsoftheleadwiretogether. IftheLEDfailstolight(theLEDisnothighly visibleunderbrightsunlightconditionsitmaybe necessarytoshadetheLEDwithyourhandtobe certainthatthelightisoperating)orthebuzzerfails tosoundasaresultoftheprevioustests,checkthe following: 1.Battery:Besurethatthebatteryisafresh9V transistorbattery.Checkthatthepositiveand negativeterminalsareconnectedcorrectly. 2.Mechanical(solder)connections:Anohmmeter willbehelpfulforthesechecks.Checkeachleg oftheleadwiretoassurethatitconducts electricity.Thewiremaybebrokenor connectionsmaybeimproperlymade.Make certainblobsofsolderarenotmakingunwanted connections.Thencheckallothersolder connectionsbetweenthebattery,switch,and electroniccomponents.Checkthatcontactis madewhentheswitchisclosed. 3.Circuitelectricalcomponents:Ifthewaterlevel indicatorstilldoesnotworkaftertheprevious checks,carefullycheckorientationsofcritical components(transistor,LED)toinsuretheywere installedproperly.Ifthisdoesnotremedythe problem,oneofthepartsmaybedefective:a componentmayhavebeendamagedby overheatingorperhapswasdefectivewhen purchased.Thesecomponentscanbetestedby closingtheswitchtoprovidebatterypowertothe circuitandshortingacrossleadsCandEofthe transistor(Figure2c).IftheLEDlightsduring thistest,thenthetransistorisdefective.Ifthe LEDdoesnotlightduringthetest,replacethe LEDandtrythetestagaintodeterminewhether thetransistorisalsodefective.Fortunately,these componentsarenotexpensive. Oncethecircuithasbeentestedandfoundtobe functional,coatbothsidesoftheboardwithsealant toprolongthelifeofyourwaterlevelsensor.Donot allowthesealanttogetinsidethebuzzer;otherwise, itwillnotfunctionproperly,ifatall.For convenience,theexperimenter'sboxcanallbe mountedononeendofthereelunitasillustratedin Figure1.Thiscanbedonewithmachinescrewsand nuts(donotallowsharpedgesofthescrewsto projectintothewirearea).Careshouldbetaken whenoperatingthedevicetopreventwaterfrom gettinginsidethebuzzer,becausethiswillshortenits life.

PAGE 6

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page6USEOFTHEWATERLEVELINDICATOR Figure4.Fielduseofthewaterlevelindicator. Aftertesting,thewaterlevelindicatorisreadyfor fielduse.Theinstrumentisusedbyloweringthe weightedsoundingwireintothespacebetweenthe wellcasingandthedischargepipeasshowninFigure 4.Thisspaceshouldbeaccessiblethroughthewell sealoncommonly-usedsubmersible,turbine,andjet pumpingsystems. Ondeep-wellturbinepumpsanaccessport (manufacture'sinspectionport)onthepump dischargeheadshouldprovideaccesstothewell (Figure5).Mostmanufacturershaveincludedthe accessportinthedesignofthedischargehead.Note thattheportprovidesaccesstothespacebetweenthe wellcasingandthecolumnpipe.Theremayalsobe portsonthedischargeheadforaccesstothecolumn pipe.Donotlowerthewaterlevelindicatorwireinto thecolumnpipebecauseitwillbecomeentangled withthedriveshaftwhenthepumpisstarted. Todeterminewhethertheaccessportyouhave locatedistheproperone,removetheplugandstart thepumpwithoutinsertingtheleadwire.Ifwateris dischargedfromthisport,itisnotthecorrectaccess tothewell.(CAUTION:Watermaybesprayed throughoutthepumphouse.Attachanadapterand ahosetoroutethewaterawayfromtheareato preventdangerfromelectricalshockorother hazards.)Ifnowaterisdischargedfromtheopen Figure5. Soundingtubeandmanufacturer'sinspection portlocationsonaturbinepumpinadeepwell. port,thentheleadwirecanbeloweredintotheprot tomeasurewaterlevelinthewellwhilethepumpis operating. Unfortunately,manypumpingsystemsdonot providereadyaccesstothewelltomeasurewater levels.Theaccessportifoftenpluggedor inaccessibleduetoimproperpumpinstallation.In thosecases,itmaybenecessarytodrillintothe casing(perhapsthroughtheconcreteslab)toinstall anaccess"sounding"tubeasshowninFigure5. Insomecases,itwillnotbepossibletomakea watertablemeasurementinthespacebetweenthe columnpipeandthecasingpipe.Thisistrueifthe pipeswerenotproperlysizedandthereisnotenough spacebetweenthetwopipestoloweraprobeto makethemeasurement.Inthatcase,itwillnotbe possibletomakeawatertablemeasurementusing thisinstrument.WaterlevelMeasurementsThewaterlevelindicatorcanbeusedtomeasure thedepthtowaterinawellundereitherstaticor pumpingconditions.Thestaticwaterlevelisthe levelinthewellwhenthepumpisnotoperatingand hasnotbeenoperatingforaperiodoftime.

PAGE 7

MeasuringWaterLevelsinWells:AnInexpensiveElectricWaterLevelIndicator Page7Thepumpingwaterlevelisthatwhichis measuredwhenthepumpisoperating.The differencebetweenstaticandpumpingwaterlevelsin thewelliscalleddrawdown.InFlorida,drawdowns aretypically5to10feet,butmayrangefrom0to30 or40feet.Smallerdrawdownsindicatebetter yieldingwells,thatis,wellswhichareabletosupply therequiredflowratesmorereadily.Smaller drawdownsaredesirablebecausewaterwillnotneed tobeliftedasfartothegroundsurface.Therefore, lessenergywillberequiredforpumping.SafetySafetyshouldalwaysbeaconsiderationwhen workingwithmechanicalsystems.Unfortunately,the accessportsforwaterlevelmeasurementsareoften nearthepumpdriveshaftonthepumpdischarge head.Ifmeasurementsofpumpingwaterlevelare beingmade,theshaftwillbeturningatahighrateof speed.Keephands,clothing,andthewaterlevel indicatorsoundingwiresawayfromthespinningshaft. Ifnecessary,installashieldbetweentheshaftandthe areainwhichyouareworking.SUMMARYDetailsweregivenfortheconstruction,testing, anduseofaninexpensiveelectricwaterlevel indicatorforthemeasurementofwaterlevelsinwells. Thisinstrumentcanbeconstructedbyindividuals withaveragemechanicalskillsandwithoutin-depth knowledgeofelectronics.Thewaterlevelindicator canbeusedtoobtaininformationnecessaryforpump performancetesting,welltesting,pumpselectionand installation,andaquifertesting.