Information for Homeowners

How Cleaners Affect Septic Tanks
Several manufacturers of septic tank additives claim improper functioning of residential septic tank systems is caused by adding household cleaners to the septic system. They claim that bacterial additives are needed to resupply the bacterial population required for anaerobic digestion in the septic tank.


However, the bacteria responsible for the digestion in the septic tank are commonly found in the domestic wastewater entering the tank as well as the soil of the drain field. As long as the septic tank is being used and maintained properly, the incoming wastewater from the residence will supply the septic tank with enough bacteria to properly carry out digestion.

Household Cleaning Products
Research conducted over the past several years has concluded that with normal use, household cleaning products do not adversely affect septic tank operation. Normal use of household cleaning products is considered to be the amount recommended by the manufacturer.

With normal use, household cleansers and disinfectants perform well in destroying bacteria in the home, but do not harm the bacterial action required for a septic tank to operate properly. This is due to dilution of the cleaning products once they enter the tank and the absorptive capacity of the organic material in it.

Study Results
A study conducted at the University of Arkansas at Little Rock determined the amount of household chemicals required to destroy the bacterial population in an individual domestic septic tank. Domestic cleansers, disinfectants, and drain-openers were selected to represent commonly used cleaning products.

Results of this study showed that an excessive amount of any of the cleansers or disinfectants applied in a slug loading (all at once) was required to destroy the bacteria in the septic tank. However, after normal septic system usage, the bacterial population recovered to its original concentration within hours. In other words, under extreme stress and shock loading conditions, the bacteria can be destroyed in the septic tank. Rejuvenation does occur, however, within hours following normal system usage.

Drain Cleaners
The study showed that even minute amounts of the drain-openers can kill off the bacterial population in the septic tank. Therefore, the recommendation was made not to use large amounts of drain cleaners.

Recommended Doses of Cleaner
Recommended doses not to be exceeded for a 1,000-gallon septic tank were 1.3 gallons of bleach, 2.5 gallons of cleansers or disinfectants, and 0.65 ounces of drain-openers. Higher doses were found to affect the septic tank bacterial populations.

If you are concerned about the effects of the cleaning products on your septic system, there are alternatives available. Penn State University has developed a fact sheet that lists several basic cleaning ingredients, along with steps to follow, that may be used for normal household cleaning jobs. For example:
  • White vinegar can be used as a cleaner, deodorizer, or grease cutter
  • Lemon can be used also as a cleaner, deodorizer, or stain remover
  • Use of one-fourth cup baking soda, one-half cup vinegar, and one gallon of boiling water can clear most household drain blockages
*Article from National Small Flows Clearinghouse - Winter 1995