Septic Tank Maintenance

Care & Maintenance

Septic tanks should be cleaned before too much sludge or scum is allowed to accumulate. If the top of the sludge or the bottom of the scum approaches too close to the outlet, solids will be carried out of the tank into the absorption field and may clog the pores in the field. Eventually, liquid may break through to the ground surface or the sewage may not flow from the house. When this occurs the tank should be pumped; it may also be necessary to construct a new lateral field if the lines are clogged with solids. The Health Department must be notified of all failures.

The frequency of cleaning depends on the size of the septic tank and the number of people it serves. When a garbage grinder is used, more frequent cleaning will be required. Septic tanks should also be checked yearly but with ordinary use and care, a septic tank may last 2 to 3 years between cleanings. However, in many cases septic tanks can satisfactorily operate even longer. The homeowner should make measurements and decide for himself when his tank needs cleaning.

When the bottom of the scum is within 3 inches of the bottom of the outlet device or the top of the sludge is within the limits of the following table, the tank should be cleaned. A long stick wrapped with a towel and lowered to the bottom of the tank will show the depth of the sludge and the liquid depth of the tank. Scum is measured with a stick and weighted hinged flap. The stick is lowered through the scum and the hinged flap falls into the horizontal position. The stick is then raised until resistance is felt. With the same tool, the distance to the bottom of the device can be found.

Notes: excessive use of water could over-load the capacity of the absorption field.

Allowable Sludge Accumulation


Liquid Depth 2.5 feet 3 feet 4 feet 5 feet
Liquid cap. Distance from bottom of the outlet
Tank Device to the top of the sludge in inches
750 5 6 10 13
900 4 4 7 10
1,000 4 4 6 8

Helpful Tips


  • Chemical should not be added to the septic tanks. Small quantities of household cleaners are okay.
  • Limit water use during wet periods
  • Every property should keep measurements on location of tank and laterals. (Draw Map)
  • Don't connect sump pump lines to the septic system.
  • Dates of septic tank cleanings should be kept.
  • Keep non-biodegradable items out of the system (cigarette butts, sanitary napkins, coffee grounds, cooking fats, bones, wet strength towels, disposable diapers, facial tissues, cat litter)
  • Toilets should not be allowed to run
  • Keep all paint, solvents and pesticides out of the system. These chemicals can seep into well water.
  • Heavy vehicles (cars, etc.) should not be driven over absorption area.
  • Septic tank additives are not recommended. None will "fix" a failing system.
  • Don't introduce toxic wastes into the system.
  • Low phosphorus detergents from washers will not impede bacterial action in the tank and absorption area.
  • Yeast does not improve operation.
  • Water from downspouts and terrain should be channeled away from tank and absorption area.
  • The life of the absorption field will be shortened if tank is not cleaned periodically; once every 4 years is recommended.
  • Smaller tanks and garbage grinders increase cleaning frequency.
  • Grease traps are not usually necessary.