SEPTIC TANKSSEPTIC TANKS

Model Decentralized Wastewater Model Decentralized Wastewater Practitioner CurriculumPractitioner Curriculum

NDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized Water This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with Resources Capacity Development Project (NDWRCDP) with

funding provided by the U.S. Environmental Protection Agency funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881through a Cooperative Agreement (EPA No. CR827881--0101--0) 0) with Washington University in St. Louis. These materials have with Washington University in St. Louis. These materials have

not been reviewed by the U.S. Environmental Protection not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents representatives of the NDWRCDP. The contents

of these materials do not necessarily reflect the views and of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. policies of the NDWRCDP, Washington University, or the U.S.

Environmental Protection Agency, nor does the mention of trade Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or names or commercial products constitute their endorsement or

recommendation for use.recommendation for use.

CIDWT/University DisclaimerCIDWT/University DisclaimerThese materials are the collective effort of individuals from These materials are the collective effort of individuals from

academic, regulatory, and private sectors of the academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have onsite/decentralized wastewater industry. These materials have

been peerbeen peer--reviewed and represent the current state of reviewed and represent the current state of knowledge/science in this field. They were developed through a knowledge/science in this field. They were developed through a

series of writing and review meetings with the goal of series of writing and review meetings with the goal of formulating a consensus on the materials presented. These formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of materials do not necessarily reflect the views and policies of

North Carolina State University, and/or the Consortium of North Carolina State University, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). Institutes for Decentralized Wastewater Treatment (CIDWT).

The mention of trade names or commercial products does not The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from constitute an endorsement or recommendation for use from

these individuals or entities, nor does it constitute criticism these individuals or entities, nor does it constitute criticism for for similar ones not mentioned.similar ones not mentioned.

CitationCitation

Loudon, T.L., T.R. Bounds, J.C. Converse, T. Loudon, T.L., T.R. Bounds, J.C. Converse, T. Konsler and C. Rock. 2005. Septic Tanks Konsler and C. Rock. 2005. Septic Tanks ––PowerPoint Presentation. PowerPoint Presentation. inin (D.L. Lindbo and (D.L. Lindbo and N.E. Deal eds.) Model Decentralized N.E. Deal eds.) Model Decentralized Wastewater Practitioner Curriculum. National Wastewater Practitioner Curriculum. National Decentralized Water Resources Capacity Decentralized Water Resources Capacity Development Project. North Carolina State Development Project. North Carolina State University, Raleigh, NC.University, Raleigh, NC.

OverviewOverview

Typical Septic SystemTypical Septic System

evapotranspiration

septic tank

basement

soil absorption

well

treatment

ground water

streams, lakes

House

trenches

effluentbaffle

Tank FunctionsTank Functions

Solids removal by settling & Solids removal by settling & floatationfloatation

6060--80% solids removal80% solids removalAnaerobic digestionAnaerobic digestionStorage of solidsStorage of solids

Septic Tank FunctionSeptic Tank Function

SLUDGE

SCUMIN OUT

Treatment ClassesTreatment Classes

Primary Primary –– Settling and FlotationSettling and FlotationSecondary Secondary –– Usually aerobic Usually aerobic biological treatmentbiological treatmentAdvanced Advanced –– Enhanced nutrient Enhanced nutrient removal and disinfectionremoval and disinfection

Anaerobic DigestionAnaerobic Digestion

ORGANICMATTER GASES + HUMUS

CO2CH4H2SNH3

Biological Activities in the Septic Biological Activities in the Septic TankTank

Anaerobic (without Oxygen)Anaerobic (without Oxygen)Anaerobic digestion isAnaerobic digestion is

IncompleteIncompleteCheap and easyCheap and easyReliableReliable

Gases produced are odoriferousGases produced are odoriferousNot all solids in the tank are biodegradableNot all solids in the tank are biodegradable

Factors That Influence Factors That Influence Anaerobic DigestionAnaerobic Digestion

pHpHChemicalsChemicalsHighly variable flow patternsHighly variable flow patternsPharmaceuticals Pharmaceuticals Process wastewatersProcess wastewatersLack of tank maintenanceLack of tank maintenance

Factors That Influence Factors That Influence Wastewater StrengthWastewater Strength

FOGsFOGsFlow pattern Flow pattern Flow ratesFlow ratesNonbiodegradable itemsNonbiodegradable items

Tank DesignTank Design

Septic Tank DesignSeptic Tank Design

SizingSizingGeometryGeometryCompartmentsCompartmentsVehicular TrafficVehicular TrafficAppurtenancesAppurtenances

Effective Volume (new tank)Effective Volume (new tank)

Baffle

Effective Volume

Riser

Cleanout Pipe

Tank SizingTank Sizing

Generally prescribed by the permitting Generally prescribed by the permitting agency for individual homes based on agency for individual homes based on home sizehome sizeCriteria: Hydraulic detention time plus Criteria: Hydraulic detention time plus solids storagesolids storage

1 to 2 days detention of design flow1 to 2 days detention of design flowAdd solids storage volume equal to 1/3 Add solids storage volume equal to 1/3 –– 1/2 1/2 of the above hydraulic detentionof the above hydraulic detention

Septic Tank Sizing ExampleSeptic Tank Sizing ExampleConsider a 3 Consider a 3 –– bedroom homebedroom homeDesign flow: 3 br, 2 people/br, 75 gpd/personDesign flow: 3 br, 2 people/br, 75 gpd/person

Flow = 3 x 2 x 75 gpd = 450 gpdFlow = 3 x 2 x 75 gpd = 450 gpdProvide for 2 day detention => 2 x 450 = 900 galProvide for 2 day detention => 2 x 450 = 900 gal

Add solids storage Add solids storage 1/3 of the above = 1/3 x 900 = 300 gal1/3 of the above = 1/3 x 900 = 300 gal

Total tank volume = 900 + 300 = 1200 galTotal tank volume = 900 + 300 = 1200 galThis is the minimum recommended tank sizeThis is the minimum recommended tank sizeThe tank should have two compartmentsThe tank should have two compartmentsMany regulatory agencies now require 1500 gal tank Many regulatory agencies now require 1500 gal tank for a 3for a 3--br home, but sizing starts with a procedure like br home, but sizing starts with a procedure like this.this.

Other Factors that Affect Tank SizeOther Factors that Affect Tank Size

Garbage grindersGarbage grindersAdd to solids accumulation rate and Add to solids accumulation rate and organic loadorganic loadMay add grease and oilMay add grease and oilIncrease hydraulic load someIncrease hydraulic load someThough not recommended with septic Though not recommended with septic systems, they will be used in many systems, they will be used in many homes.homes.

Other Factors that Affect Tank SizeOther Factors that Affect Tank Size

Sewage (basement) lift pumpsSewage (basement) lift pumpsWill increase turbulence in the septic Will increase turbulence in the septic tanktankShould discharge into sewer line Should discharge into sewer line –– not not directly to tankdirectly to tankTwo compartment tanks highly Two compartment tanks highly recommended with pumpsrecommended with pumpsSet pumps for minimum discharge Set pumps for minimum discharge volumesvolumes

Goal is Near Zero Velocity for Goal is Near Zero Velocity for Optimum Solids RemovalOptimum Solids Removal

Maximize distance Maximize distance between inlet and outletbetween inlet and outletLength:Width ratio at Length:Width ratio at least 3:1least 3:1Inlet to outlet drop ~ 2”Inlet to outlet drop ~ 2” Sludge

Clear Zone

Scum

Dual Chamber Septic Tank

Tank CompartmentsTank Compartments

Advantages of multiple compartmentsAdvantages of multiple compartmentsMore complete solids removalMore complete solids removalImproved effluent qualityImproved effluent qualityProtect against solids discharge due to Protect against solids discharge due to lack of maintenance lack of maintenance

Two Compartment TankTwo Compartment Tank

2/3 total volume

1/3 total volume

Tank CompartmentsTank Compartments

Meander Tank ExampleMeander Tank Example

INLET

OUTLET

Baffles

Advantages of a meander tank• Longer flow path• Opportunities to drop solids as flow turns• Most solids are removed in first chamber

Vehicular TrafficVehicular Traffic

Standard concrete tanks are not designed Standard concrete tanks are not designed to handle traffic loadsto handle traffic loads

ASTM Standard CASTM Standard C--857 provides information 857 provides information on these design issueson these design issues

Using other tanks in areas subject to traffic Using other tanks in areas subject to traffic should be done only with manufacturer should be done only with manufacturer guidance and engineer approvalguidance and engineer approval

Tank AppurtenancesTank Appurtenances

Tees and bafflesTees and bafflesEffluent screensEffluent screensAccess risersAccess risers

Inlet and Outlet Baffles/TeesInlet and Outlet Baffles/TeesOutlet baffleOutlet baffle

Assures outflow comes Assures outflow comes from clear zonefrom clear zoneHolds floating scum in the Holds floating scum in the tank

Inlet baffle Inlet baffle Directs the flowDirects the flowMinimizes turbulence and Minimizes turbulence and short circuitingshort circuiting

tank

Sludge

Clear Zone

Scum

Dual Chamber Septic Tank

TeeTee--type baffle outlettype baffle outlet

Baffle made from sanitary Baffle made from sanitary tee and 4tee and 4--in pipe nipplesin pipe nipplesPositioned directly under Positioned directly under tank opening for accesstank opening for accessSome older tanks have (or Some older tanks have (or had) teehad) tee--type baffles made type baffles made of clay or concrete pipeof clay or concrete pipe

These deteriorate and fall off These deteriorate and fall off in timein timeShould be replaced when Should be replaced when tank servicedtank serviced

Inlet baffle of concrete cast into Inlet baffle of concrete cast into tanktank

Curtain baffle Curtain baffle penetrates to well penetrates to well below liquid depthbelow liquid depthOutlet ports are made Outlet ports are made like this toolike this tooGroove at top allows Groove at top allows gas transfer across gas transfer across tank and up sewer to tank and up sewer to roof ventroof vent

Baffle formed of plastic Baffle formed of plastic fastened to tank wallfastened to tank wall

Inlet and outlet bafflesInlet and outlet baffles

Tank illustration with sealed inlet Tank illustration with sealed inlet and outlet baffles, risers to gradeand outlet baffles, risers to grade

Outlet 1Outlet 1--3” below 3” below inletSpreading of flow Spreading of flow is illustratedis illustratedFlow is Flow is attenuated attenuated

Outlet flow rate is Outlet flow rate is much less than much less than inletinletMore pronounced More pronounced in a rectangular in a rectangular tanktank

inlet

Effluent ScreensEffluent Screens

Designed to keep larger suspended solids Designed to keep larger suspended solids in the tankin the tankControl outflow rateControl outflow rateProtect the downstream componentsProtect the downstream componentsTypically replace the outlet baffleTypically replace the outlet baffleRequire riser to grade for access to screenRequire riser to grade for access to screen

Installation issuesInstallation issuesLocationLocation

TankTankSumpSumpPump vaultPump vault

Can be equipped with alarmCan be equipped with alarmScreen in second compartment of a two Screen in second compartment of a two compartment tank will require less servicecompartment tank will require less serviceShould be secure in place Should be secure in place No bypass flow if clogging occursNo bypass flow if clogging occursHousing should not interfere with normal tank Housing should not interfere with normal tank cleaning cleaning

Choosing an Effluent ScreenChoosing an Effluent Screen

Ease of serviceabilityEase of serviceabilitySize appropriately for the flowSize appropriately for the flowOpenings of 1/16 Openings of 1/16 –– 1/8 inch1/8 inchDesigned to prevent solids bypass during Designed to prevent solids bypass during cleaningcleaningLocate so that access for pumping is not Locate so that access for pumping is not hamperedhampered

Proprietary effluent screensProprietary effluent screens

Effluent Screen installed to Effluent Screen installed to replace outlet bafflereplace outlet baffle

Location of Effluent ScreenLocation of Effluent Screen

Access risersAccess risers

Provide easy access to tank and Provide easy access to tank and componentscomponentsA must for tanks containing effluent filters or A must for tanks containing effluent filters or pumpspumpsShallow tanks and short risers Shallow tanks and short risers –– the the preferred situationpreferred situation

Riser DesignRiser Design

SafetySafety

Tank ConstructionTank Construction

Tank MaterialsTank MaterialsReinforced concrete (most common)Reinforced concrete (most common)Fiberglass reinforced plastic (FRP)Fiberglass reinforced plastic (FRP)Polyethylene/polypropylene (Poly)Polyethylene/polypropylene (Poly)

Tank MaterialsTank Materials

Concrete

Fiberglas

Polyethylene

Structural SoundnessStructural SoundnessWithstand handling and transportWithstand handling and transportnot be susceptible to damage during installationnot be susceptible to damage during installationResist external and internal pressuresResist external and internal pressuresSupport a 2500# wheel load in addition to soil Support a 2500# wheel load in addition to soil loadloadTanks must be properly reinforced according to Tanks must be properly reinforced according to a standarda standard

ASTMASTMNPCANPCA

Manufacturing TanksManufacturing Tanks

Precast concretePrecast concrete

Mix DesignMix DesignStructural reinforcementStructural reinforcementManufacturing practicesManufacturing practicesJoint design Joint design Sealing materialsSealing materialsProof testing for structural soundnessProof testing for structural soundnessAccess risersAccess risersPipe penetrationsPipe penetrations

Mix DesignMix Design

Low water to cement ratioLow water to cement ratioMinimum compressive strength of 4000 Minimum compressive strength of 4000 psi after 28 dayspsi after 28 daysQuality aggregatesQuality aggregates

Consistent gradationConsistent gradationLow moisture contentLow moisture contentFree from deleterious substancesFree from deleterious substances

Mix Design (continued)Mix Design (continued)

Appropriate use of chemical admixtures to Appropriate use of chemical admixtures to improve:improve:

Mix flowabilityMix flowabilityWater reductionWater reductionAir EntrainmentAir EntrainmentResistance to corrosion/degradationResistance to corrosion/degradation

Selection of proper cement typeSelection of proper cement type

Structural reinforcementStructural reinforcementReinforcement required for adequate Reinforcement required for adequate strengthstrength

Rebar Rebar –– required in toprequired in topSteel mesh Steel mesh –– may be used in walls of some may be used in walls of some tanks with cross wallstanks with cross wallsSpecial fiber, fiberglass and other materialsSpecial fiber, fiberglass and other materials

Structural reinforcement (cont.)Structural reinforcement (cont.)

Tank integrityTank integrityPrevent collapsePrevent collapse

Wire mesh in top is not enough

Structural reinforcement (cont.)Structural reinforcement (cont.)Reinforcing wire in

side wall

Proper placement of rebar in form using

“chairs”

Cutaway of tank showingrebar

Manufacturing MethodsManufacturing MethodsProper maintenance of forms or moldsProper maintenance of forms or molds

Removal of excess form oilRemoval of excess form oilRemoval of rustRemoval of rustElimination of voids to prevent spillsElimination of voids to prevent spillsMaintenance of tolerances to prevent Maintenance of tolerances to prevent improperly fitting structuresimproperly fitting structures

Manufacturing Methods (cont.)Manufacturing Methods (cont.)

Proper selection and placement of Proper selection and placement of reinforcement reinforcement Proper vibration techniques for uniform Proper vibration techniques for uniform distributiondistributionProper casting and curing to maintain Proper casting and curing to maintain correct moisture content and temperaturecorrect moisture content and temperature

Joint Design for Joint Design for Concrete TanksConcrete Tanks

Mid-seam

Top seam

“Monolithic” Concrete Tanks“Monolithic” Concrete Tanks

Sealing Materials for Precast TanksSealing Materials for Precast Tanks

Blended sealant compoundsBlended sealant compoundsButylButyl--rubber basedrubber basedAsphaltAsphalt--based (bituminous)based (bituminous)

Mastic: Rules of thumbMastic: Rules of thumb

Quality mastic does not compress much Quality mastic does not compress much between thumb and forefingerbetween thumb and forefingerCompressibility in coldCompressibility in cold--weather weather installationsinstallationsShould not shred or snap when handShould not shred or snap when hand--stretchedstretchedHigher is better than wider: 50% Higher is better than wider: 50% compression is desirablecompression is desirableKnead joined ropes prior to placementKnead joined ropes prior to placement

Concrete Tank SeamsConcrete Tank SeamsAchieving a Achieving a watertight joint: watertight joint:

Seams must be Seams must be smooth, clean and smooth, clean and drydryHigh quality mastics, High quality mastics, seal gaskets seal gaskets Proper placement of Proper placement of masticmastic

Concrete Tank Seams (cont.)Concrete Tank Seams (cont.)Achieving a watertight joint: Achieving a watertight joint:

Extra butyl rubber wrap around jointExtra butyl rubber wrap around jointJoint must be tested to be sure it does not leakJoint must be tested to be sure it does not leak

Proof Testing for Structural Proof Testing for Structural SoundnessSoundness

Tanks should reach 4000 psi before Tanks should reach 4000 psi before delivery to sitedelivery to siteShould comply with ASTM and NPCA Should comply with ASTM and NPCA standardsstandardsOther engineering tests also availableOther engineering tests also available

Access Risers for Precast TanksAccess Risers for Precast Tanks

Made from various materialsMade from various materialsCastCast--inin--place or added after tank place or added after tank constructionconstruction

CastCast--inin--place concrete risersplace concrete risers

CastCast--inin--place poly risersplace poly risers

Adding concrete risersAdding concrete risers

Mastic provides a better seal than mortar.

Adding concrete risers (cont.)Adding concrete risers (cont.)

Adding poly risers to concrete Adding poly risers to concrete tankstanks

Adapter rings for riser attachment can be Adapter rings for riser attachment can be castcast--in place or bolted in placein place or bolted in place

Adding poly risers to concrete Adding poly risers to concrete tankstanks

Riser can then be attached to adapter Riser can then be attached to adapter using adhesive and stainless boltsusing adhesive and stainless bolts

Pipe Penetrations : Rubber Boot Pipe Penetrations : Rubber Boot SealsSeals

Boot may be cast Boot may be cast into the tank or into the tank or pressed into a pressed into a smooth hole with an smooth hole with an expanding clamp.expanding clamp.Stainless steel hose Stainless steel hose clamp seals boot to clamp seals boot to pipepipeFlexible Flexible –– allows allows some pipe some pipe movement but movement but maintains sealedmaintains sealed

Plastic pipe penetration sealsPlastic pipe penetration seals

CastCast--in plastic fittingin plastic fittingFlexible Flexible –– allows allows some pipe movementsome pipe movement

PVC Pipe Penetration SealPVC Pipe Penetration Seal

CastCast--in PVC fitting in PVC fitting Connecting pipe Connecting pipe cements into fittingcements into fittingInflexible connectionInflexible connectionPipe will need Pipe will need support during support during backfillbackfillStress created if any Stress created if any settling occurssettling occurs

Polyethylene/polypropylene Septic Polyethylene/polypropylene Septic TanksTanks

Tank Construction: PolyTank Construction: Poly

Rotationally moldedRotationally moldedOneOne--piece piece constructionconstruction

Pipe seals and access risers for Pipe seals and access risers for poly tankspoly tanks

FiberglassFiberglass--reinforced Plastic (FRP) reinforced Plastic (FRP) Septic TanksSeptic Tanks

Tank Construction: FiberglassTank Construction: FiberglassOneOne-- or twoor two--piece constructionpiece construction

TwoTwo--piece FRP Tank Constructionpiece FRP Tank Construction

Assembling tank halvesAssembling tank halves

Joining 2Joining 2--piece fiberglass tankspiece fiberglass tanks

Pipe seals for FRP tanksPipe seals for FRP tanks

Access Risers for FRP tanksAccess Risers for FRP tanks

Overall Quality of Septic Tanks Overall Quality of Septic Tanks

Looks aren’t everything Looks aren’t everything

Cosmetic deficiencies may not affect Cosmetic deficiencies may not affect performanceperformanceGoodGood--looking tanks may have structural looking tanks may have structural deficienciesdeficiencies

Summary: What to look for in Summary: What to look for in concrete tanksconcrete tanks

Reasonably smooth surface Reasonably smooth surface No honeycombing or cracksNo honeycombing or cracksNo efflorescenceNo efflorescenceNo exposed rebar or wire inside or outsideNo exposed rebar or wire inside or outsideSmooth, well made tongue and groove or Smooth, well made tongue and groove or shiplap joint with masticshiplap joint with masticFlexible, watertight pipe seals at all pipe Flexible, watertight pipe seals at all pipe penetrationspenetrationsCastCast--inin--place or mechanicallyplace or mechanically--attached riser attached riser with tight fitting lidwith tight fitting lid

Summary: What makes a good Summary: What makes a good poly tank?poly tank?

Even wall thickness Even wall thickness –– no thin areasno thin areasNo pin holesNo pin holesNo deformation of riser openingsNo deformation of riser openingsFlexible pipe seals at all pipe penetrationsFlexible pipe seals at all pipe penetrationsMechanically attached riser with tight Mechanically attached riser with tight fitting lidfitting lid

Summary: What makes a good Summary: What makes a good fiberglass tank?fiberglass tank?

Properly sealed midProperly sealed mid--seamseamNo imperfections in layNo imperfections in lay--up up No deNo de--lamination lamination No cracks and dings from handlingNo cracks and dings from handlingFlexible pipe seals at all pipe penetrationsFlexible pipe seals at all pipe penetrationsMechanically attached riser with tight Mechanically attached riser with tight fitting lidfitting lid

Problems with nonProblems with non--concrete tanksconcrete tanks

Ultimately, it is essential to TEST.Ultimately, it is essential to TEST.

GoodGood--looking tanks may have defectslooking tanks may have defectsPoor appearance does not necessarily Poor appearance does not necessarily indicate problemsindicate problemsIrregularities in tank of any material should Irregularities in tank of any material should be investigated thoroughlybe investigated thoroughlyIf unsure, consult with manufacturer or If unsure, consult with manufacturer or engineerengineerTesting will ensure quality, watertight Testing will ensure quality, watertight installations.installations.

Tanks must be watertightTanks must be watertight

Exfiltration could release untreated Exfiltration could release untreated sewage deep in the soil sewage deep in the soil Infiltration may occurInfiltration may occur

Disrupt settlingDisrupt settlingOverload drainfield or downstream Overload drainfield or downstream componentscomponents

Possible points of leakagePossible points of leakage

Weep holes at the base of the tankWeep holes at the base of the tankMidMid--seam jointseam jointInlet/outlet pipe penetrationsInlet/outlet pipe penetrationsTopTop--seam jointseam jointTank top/access riser jointTank top/access riser jointAccess riser/lid jointAccess riser/lid jointAny damaged, improperlyAny damaged, improperly--formed location formed location or area where material is too thin.or area where material is too thin.

Watertightness Watertightness

Dual Chamber Septic Tank:Points of Infiltration

Watertight sealsWatertight sealsAll jointsAll jointsPipe penetrationsPipe penetrationsRiser and lidRiser and lid

Watertightness Testing Watertightness Testing

Hydrostatic (water) testing Hydrostatic (water) testing Vacuum testingVacuum testing

Hydrostatic TestingHydrostatic Testing

Prior to backfillingPrior to backfillingCap pipesCap pipesFill 2” into riserFill 2” into riserSoak for 24 hrsSoak for 24 hrsRefill if concreteRefill if concreteCheck in 24 hrsCheck in 24 hrsAllowable loss is Allowable loss is less than one less than one gallongallon

Water Test

Less Than 2"

Vacuum TestingVacuum Testing

Pipe seal

Vacuum pump

Plate seal to top of riser or

tankGage to

measure vacuum

Checking Existing Tanks for Checking Existing Tanks for WatertightnessWatertightness

Care is needed in preparation for testCare is needed in preparation for testHave to plug inlet and outletHave to plug inlet and outletMust have no flow Must have no flow

Could then either water or vacuum testCould then either water or vacuum test

Checking Existing Tanks for Checking Existing Tanks for WatertightnessWatertightness

Other physical evidenceOther physical evidenceRoot intrusionRoot intrusionOutflow when there is no inflowOutflow when there is no inflowEvidence of fluctuating water levels Evidence of fluctuating water levels High water table area:High water table area:•• Pump during wet season and look for infiltration Pump during wet season and look for infiltration •• Beware of flotation Beware of flotation

Excavate outside of the tank and look for Excavate outside of the tank and look for evidence of exfiltration evidence of exfiltration –– blackness, odor, etc.blackness, odor, etc.

Tank InstallationTank Installation

Safety Safety

Maintain a safe working environment: Maintain a safe working environment: comply with OSHA standardscomply with OSHA standardsProtect excavations from sidewall collapseProtect excavations from sidewall collapse

Excavate backExcavate backUse trench boxesUse trench boxes

Stay safely clear of the tank during Stay safely clear of the tank during installationinstallation

Safety (cont.)Safety (cont.)Use proper slingsUse proper slingsSlings properly placed in grooves prepared by Slings properly placed in grooves prepared by the manufacturer for handling the tankthe manufacturer for handling the tank

Planning and ExcavationPlanning and Excavation

Check building stubCheck building stub--out elevationout elevationTanks should be kept as shallow as Tanks should be kept as shallow as possiblepossible

Minimize soil pressureMinimize soil pressureMinimize potential of ground water Minimize potential of ground water effectseffectsKeep soil treatment system as shallow Keep soil treatment system as shallow as possibleas possible

Planning and Excavation (cont.)Planning and Excavation (cont.)

Tank must be set levelTank must be set levelBuilding sewer must slope 1Building sewer must slope 1--2% 2%

(1/8 (1/8 –– ¼” per foot)¼” per foot)Know tank dimensions before Know tank dimensions before excavationexcavation

Planning and Excavation (cont.)Planning and Excavation (cont.)

Set tank on undisturbed material or Set tank on undisturbed material or granular beddinggranular beddingAlways work safely!Always work safely!

Bedding MaterialBedding Material

Setting the Tank and Setting the Tank and Joining SeamsJoining Seams

Tank must Tank must be set levelbe set level

Setting the Tank and Joining Setting the Tank and Joining SeamsSeams

All workers should be safely positioned All workers should be safely positioned relative to suspended tanks during relative to suspended tanks during installation.installation.

Installation of twoInstallation of two--piece concrete piece concrete tankstanks

Handling and Handling and installing two piece installing two piece tanks to assure no tanks to assure no leaksleaks

Mating tank edges Mating tank edges must not be damagedmust not be damagedProper sealant must Proper sealant must be used and correctly be used and correctly placedplaced

Applying masticApplying mastic

Undamaged edges Undamaged edges must be properly fit must be properly fit togethertogether

Mastic uniformly Mastic uniformly compressed compressed Watertight seal Watertight seal properly formedproperly formed

Tanks must be Tanks must be carefully set to carefully set to avoid damage avoid damage during during installationinstallation

Setting the TankSetting the Tank

Backfilling the Backfilling the InstallationInstallation

High Water High Water Table Table

ConditionsConditions

Pipe PenetrationsPipe PenetrationsPenetrations must be Penetrations must be water tight after water tight after backfillbackfillUse Sch 40 PVC or Use Sch 40 PVC or stronger across stronger across excavationsexcavationsTamp the soil under Tamp the soil under the pipe for supportthe pipe for supportFlexible boot seals Flexible boot seals recommendedrecommended

Questionable SealsQuestionable Seals

Proper final grade: access risers to Proper final grade: access risers to the surfacethe surface

Slopes Away From Riser and Tank in all Directions

Operation and MaintenanceOperation and Maintenance

Operation and MaintenanceOperation and Maintenance

In most cases, the homeowner is the In most cases, the homeowner is the operatoroperatorHomeowners need basic information on Homeowners need basic information on operationoperation

How the system worksHow the system worksHow to use the systemHow to use the systemWhat should not be put into septic systemsWhat should not be put into septic systems

Homeowner must be encouraged toHomeowner must be encouraged toHave the system inspected periodicallyHave the system inspected periodicallyPump the tank as neededPump the tank as needed

Operation and Maintenance of Operation and Maintenance of Septic TanksSeptic Tanks

Solids accumulate in septic tanksSolids accumulate in septic tankssludge in the bottom sludge in the bottom scum on topscum on top

Pump before solids begin to increase in Pump before solids begin to increase in the effluentthe effluent

Frequency Of PumpingFrequency Of Pumping

Calendar recommendationCalendar recommendationEvery 3Every 3--5 years5 years

As needed As needed Measurement of sludge and scumMeasurement of sludge and scum

Determining Need for PumpingDetermining Need for Pumping

Sludge

Total Clear Space

Liquid Level

Scum

Outlet

Sludge Clear Space (9" min.)

Scum Clear Space (3" min.)

Pump when:• scum clear space is <3” or• sludge clear space is <9”

Measuring Measuring ScumScum

Devices for Measuring SludgeDevices for Measuring Sludge

???? Clear plastic tube with a foot valve on the end

Infrared eye on a pole

Pumping as Needed According Pumping as Needed According to Actual Measurementto Actual Measurement

Not done muchNot done muchMost tanks are buried Most tanks are buried –– no riser to gradeno riser to grade“If you have to dig up the tank, you might as “If you have to dig up the tank, you might as well just pump it”well just pump it”Lack of skillLack of skill

Opinions vary on frequencyOpinions vary on frequencyMay be dictated by state regulationMay be dictated by state regulationRecommendations here are based on actual Recommendations here are based on actual measurements of when accumulated solids measurements of when accumulated solids affect effluent quality affect effluent quality ––i.e. sciencei.e. science

46912

Pump-out interval (yrs)4579

Pump-out interval (yrs)

8765Number of occupants 8765

Number of occupants

1500Capacity (Gallons)1500

Capacity (Gallons)

591425

Pump-out interval (yrs)4711

22

Pump-out interval (yrs)

5432Number of occupants 5432

Number of occupants

1000Capacity (Gallons)1000

Capacity (Gallons)

US Public Health Service (1955)

Glide Effluent Sewer (1987)

Always be safeAlways be safe

Beware of pumping tanks Beware of pumping tanks during times of high water table during times of high water table conditionsconditions

Tank Inspection at Time of Tank Inspection at Time of PumpingPumping

Tank should be thoroughly inspectedTank should be thoroughly inspectedDamaged or missing bafflesDamaged or missing bafflesGeneral tank deteriorationGeneral tank deterioration

•• especially in the head space above the water levelespecially in the head space above the water levelHoneycomb in concrete surfaceHoneycomb in concrete surfacePin holes or nonPin holes or non--uniform wall thickness in fiberglass uniform wall thickness in fiberglass or plasticor plasticRoot intrusion Root intrusion

Root Intrusion Root Intrusion

Tank Inspection at Time of Tank Inspection at Time of PumpingPumping

Other indications of leaksOther indications of leaksFluctuating tank levelsFluctuating tank levelsDamaged seamsDamaged seamsCracks Cracks

Consider adding an effluent screen Consider adding an effluent screen Inspect risers and lids for leakage or damageInspect risers and lids for leakage or damage

Additional ConsiderationsAdditional ConsiderationsTwo compartment tanks: open and inspect Two compartment tanks: open and inspect both chambersboth chambersPumping too often may be detrimentalPumping too often may be detrimental

Normal development of scum and sludge Normal development of scum and sludge layerslayersNormal population of beneficial microbes Normal population of beneficial microbes Increased the burden of septage disposal Increased the burden of septage disposal Unnecessarily adds to cost for ownerUnnecessarily adds to cost for owner

Servicing Effluent ScreensServicing Effluent Screens

Clean screen when Clean screen when pumping tankpumping tankWash material back Wash material back into tankinto tankIf cleaned at other If cleaned at other times:times:

Remove and clean Remove and clean elsewhereelsewhereClean over inlet endClean over inlet endNo solids bypassNo solids bypass

Effluent Screen CleaningEffluent Screen Cleaning

Wear gloves!Wear gloves!Wash off directly into Wash off directly into the inlet endthe inlet endSolids bypass Solids bypass protectionprotection

Effluent Screen CleaningEffluent Screen Cleaning

Often, a tool is needed to remove the screen for Often, a tool is needed to remove the screen for cleaning and then to replace it into the housingcleaning and then to replace it into the housingNote that riser opening allows easy access to filterNote that riser opening allows easy access to filter

Factors that Increase Screen Factors that Increase Screen Cleaning FrequencyCleaning Frequency

High fat, oil and grease in sewageHigh fat, oil and grease in sewageExtensive hair or laundry lintExtensive hair or laundry lintBackwash from water softenerBackwash from water softenerHigh water usage or high peak flowsHigh water usage or high peak flowsScreen too small for the applicationScreen too small for the application

Excessive screen clogging may Excessive screen clogging may indicate:indicate:

Lack of proper biological activity in the Lack of proper biological activity in the tanktankExcessive flowsExcessive flows

InfiltrationInfiltrationLeaky plumbing fixturesLeaky plumbing fixtures

Neglecting to pump the tank when neededNeglecting to pump the tank when needed

Myths and AdditivesMyths and AdditivesTanks typically do not require additivesTanks typically do not require additives

No need to “start” a tank with a dead chickenNo need to “start” a tank with a dead chickenAdding yeast, while harmless, is not neededAdding yeast, while harmless, is not neededCommercial additives are normally not neededCommercial additives are normally not needed

Beware of any additive that suggests it will Beware of any additive that suggests it will reduce pumping frequencyreduce pumping frequency

Normal function means some accumulation Normal function means some accumulation •• Nonbiodegradables Nonbiodegradables –– e.g. synthetic fabric linte.g. synthetic fabric lint

Solids may be washed out to next downstream Solids may be washed out to next downstream treatment componenttreatment componentIndependent research shows no benefitIndependent research shows no benefit

Recommendations to HomeownersRecommendations to Homeowners

Things In The Tank That Degrade Things In The Tank That Degrade Slowly… Slowly…

…and accumulate as scum…and accumulate as scumToilet paperToilet paperHairHairLaundry lintLaundry lintOIL and GREASE OIL and GREASE

What Does What Does NotNot Belong In The Belong In The Tank?Tank?

Cigarette buttsCigarette buttsCoffee groundsCoffee groundsCooking fatsCooking fatsPaints & chemicalsPaints & chemicalsPaper towelsPaper towelsFemale sanitary productsFemale sanitary productsDisposable diapersDisposable diapersCondomsCondoms

Septic System Use Septic System Use RecommendationsRecommendations

Avoid simultaneous dischargesAvoid simultaneous dischargesShowers, washing clothes and running the Showers, washing clothes and running the dishwasher all at oncedishwasher all at once

Spread laundry out Spread laundry out –– avoid consecutive loads, avoid consecutive loads, Install a laundry lint filter Install a laundry lint filter Keep nonKeep non--sewage water out of the systemsewage water out of the system

Water softener backwashWater softener backwashFooting drain sump pump dischargeFooting drain sump pump dischargeFloor drainsFloor drains

Inspections and TroubleshootingInspections and Troubleshooting

Procedures to determine if problems existProcedures to determine if problems exist

Must remove all lids to the tankMust remove all lids to the tankCheck if liquid level normal: at the outlet invertCheck if liquid level normal: at the outlet invert

If low, tank is leakingIf low, tank is leakingIf high, blockage or backup from drainfieldIf high, blockage or backup from drainfield

Pump the tank to determine reason for high Pump the tank to determine reason for high conditioncondition

Pipe breakage?Pipe breakage?Root intrusion?Root intrusion?Failed drainfield?Failed drainfield?

Measure sludge and scum levelsMeasure sludge and scum levels

Troubleshooting: OdorTroubleshooting: Odor

Around the septic tank Around the septic tank Check for pipe breakageCheck for pipe breakageUnsealed riser lid or inspection portUnsealed riser lid or inspection port

From roof stackFrom roof stackAbnormal development of tank biology Abnormal development of tank biology If only during still air or temperature inversion If only during still air or temperature inversion

•• Extend roof stack to above the ridgeExtend roof stack to above the ridge•• Install activated carbon filter on the stack(s) Install activated carbon filter on the stack(s)

In the houseIn the houseDrift from the roof stack?Drift from the roof stack?Dry plumbing trap?Dry plumbing trap?

Tank Abandonment ProceduresTank Abandonment Procedures

Tanks no longer used must be properly Tanks no longer used must be properly abandonedabandonedCheck local codes for requirementsCheck local codes for requirementsGoal is to render the area of the tank safeGoal is to render the area of the tank safe

Typical Abandonment ProceduresTypical Abandonment Procedures

First pump out completelyFirst pump out completelyThree possible proceduresThree possible procedures

Remove tank and properly disposeRemove tank and properly disposeCrush completely, backfill, and compact the Crush completely, backfill, and compact the soilsoilFill the tank completely with granular material Fill the tank completely with granular material or a flowable fill (concrete grout)or a flowable fill (concrete grout)

DISCUSSION AND DISCUSSION AND QUESTIONS?QUESTIONS?