Once a septic tank and absorption field are installed, you can do several things to prolong their life, thus protecting an investment which may cost 2500ormore.Hereareseveraltipsyoucanfollow.Oftenoverlookedorneglectedisthefactthatseptictanksshouldbeinspectedatleastonceannually.Ineveryproperlyfunctioningseptictank,sludgeaccumulatesinthebottom.Thissludgeiscomposedofsolidmaterialsandmustberemovedperiodically.Ifthesludgeisnotremoved,theaccumulatedsolidswillbuildupintheseptictankandwillbegintowashoutintotheabsorptionfield.Allowingsolidsfromtheseptictanktowashoutintotheabsorptionfieldwilleventuallyclogittothepointwhereanewfieldwillbeneeded.Mostauthoritiesagreethatforatypicalthree−bedroomhome,a1,000−gallon(3,800I)septictankwillneedtohavethesolidsremovedeverythreetofiveyears.Smallertanksmustbepumpedmoreoften.Septictankadditivesthatcleanthetankareavailable,butthesearegenerallynotrecommended.Someadditivesmaycausethesolidstobeflushedfromtheseptictankintotheabsorptionfield,causingcloggingproblems.Othercompoundsmayproduceaseptictankeffluentwhichwilldestroysoilstructureandcauseprematurefailureofthesoilabsorptionsystem.Todetermineifyourseptictankneedspumping,thethicknessofthesludgecanbemeasuredasillustratedinFigure1.Tomeasurethedepthofthesludge,wrapalongstickwithapieceofrough,whitetowelingandtieitsecurely.Lowerthestickthroughtheinlettee(toavoidthescum)tothebottomofthetank.Waitabout30secondsandremovethestickslowlyandcarefully.Blackparticleswillclingtothetowelindicatingthedepthofthesludge.Thesludgeshouldberemovedifitsdepthisequaltoonethirdormoreoftheliquiddepth.Occasionally,afloatingscumlayermaydevelopinseptictanks.Thisscumlayercanalsocausecloggingandshouldbecheckedannually.Thescumlayerthicknesscanbemeasuredwithastickandhingedflapdevice(Figure1).Pushthestickthroughthescumuntilthehingedflapfallsintothehorizontalposition.Raisethestickuntilyoufeelthebottomofthelayer.Markthesticktoindicatethedepthofthescumlayer.Nowusethesameproceduretolocatethelowerendofthesubmergedinletpipe.Ifthebottomsideofthescumlayeriswithinthreeinches(7.6em)ofthelowerendofthesubmergedinlet,theseptictankshouldbepumped.Mostcommunitieshavecontractorswhopumpseptictanks.Itmaycost50 or more, but it is necessary for maintaining the life of the absorption field. The contractors pump the contents into a tank truck and dispose of it at an approved treatment site or by proper land application. Be sure the workman who cleans your tank mixes the liquid, sludge and scum before pumping so that all of the material can be removed, not just the liquid. It is not recommended to wash, scrub or disinfect the septic tank when pumping. Similarly, it is not necessary to leave solids in the septic to start it again. Normally, as the septic tank fills, the natural processes begin. Products to seed the system with desirable bacteria are available, but they are also not necessary