SEPTIC TANK ADDITIVES
DANGER IN DISGUISE

NEWS FROM INDIANA STATE DEPARTMENT OF HEALTH ...

Septic Tank Additives
ISDH staff is frequently asked to comment on the use of septic tank additives. Although their use has not been addressed in our rules for on-site sewage disposal, we can provide comment on the use of septic tank additives.

A septic tank is a watertight tank designed to slow down the movement of raw sewage so that solids can separate or settle out and be broken down by bacterial action. This action does not purify the sewage, eliminate odors, or destroy all solid matter. The septic tank simply removes enough of the solids so that its effluent can be discharged to a soil absorption system without prematurely clogging the system. The septic tank will provide anaerobic digestion of organic material without the use of any additives to enhance its operation. A new septic tank does not require any special additives, because the sewage it receives contains the organisms necessary to initiate and promote anaerobic digestion.

The effective removal of solids from wastewater is only a part of the consideration in providing an on-site sewage disposal system that will function properly over an acceptable period of years. Although some solids may leave the septic tank and cause a biological mat formation in the trenches, a properly sized, designed and maintained septic tank provides acceptable solids removal without the use of additives. Much more important than the possible use of additives is proper system design and selection based on soil characteristics, careful installation practices, and proper operation by the homeowner. The use of additives will not “cure” a system if these steps are not properly followed. If these steps are properly followed, the use of additives are worthless, at best, and damaging to the system and environment, at worst.

The use of septic tank additives may be severely detrimental to the system, rather than beneficial. Joseph Salvato, Environmental Engineering and Sanitation,(1982,p.416) states that one of the causes of septic system failure is the carry-over of solids into the absorption field due to the use of septic tank additives.

The Public Health Service advises that the functional operation of septic tanks is not improved by the addition of disinfectants or other chemicals, that such compounds may result in sludge bulking, and may interfere with anaerobic digestion. The addition of chemicals is, therefore, not recommended ( Manual of Septic Tank Practice, Public Health Service, U.S. Department of Health, Education and Welfare, 1967, p.38).

The Public Health Service further states that some 1,200 products, many containing enzymes, have been placed on the market for use in septic tanks, and extravagant claims have been made for some of them. As far as is known, however, none have provided an advantage in properly controlled tests (reference same as above).

This office has received no reliable information that would counter the statements by Joseph Salvato or the Public Health Service. In fact, all information received by the office has further substantiated their statements.
After reviewing the information that has been published concerning septic tank additives, we can reach only one conclusion. Septic tank additives may clean out the tank, but the likelihood is high that they will cause failure of the absorption field due to the expulsion of large amounts of solids from the septic tank, and that some of them may pollute groundwater.

Any questions about this topic may be directed to Residential Sewage Disposal, ISDH. at (317) 233-7177.

Other Topics:
Sewage Protection Program | Caring for Your Septic System - Do's & Don'ts | Why Systems Fail | Improve Your System - Practice Water Conservation | Ten most asked questions about septic systems | Septic Systems - How they work | Check List for Evaluating Your Septic System

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