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March 9, 2006

Avoid Using Septic System Additives

Additives likely will not solve home sewage treatment system problems, a North Dakota State University water quality expert warns.

“In general, most professionals working with septic systems do not recommend using any additives,” says Tom Scherer, an NDSU Extension Service agricultural engineer.

Instead, he says, water conservation and common sense are the best ways to keeping septic systems operating. For instance, homeowners shouldn’t flush dental floss, disposable diapers, sanitary napkins, cigarette butts, plastics and other bulky nonbiodegradable wastes into the septic tank, or pour liquid fats, grease and oils down the kitchen sink. Nor should they use a garbage disposal unless the septic system is specifically designed to handle the extra load.

Many septic system problems appear in the spring, when water tables are high. Homeowners often try additives first because additive manufacturers claim their product can fix the problems, Scherer says.

Septic system additives have been sold since the 1880s. More than 120 products are on the market. The manufactures say they reduce or eliminate the need to pump the septic tank, increase bacterial action and reduce scum accumulations in the septic tank, clean the septic tank and deodorize the system, dissolve grease and other organic substances, break down fats and oils, and clear plugged drainfields.

“To determine if additives help, you first have to understand how the septic system operates,” Scherer says.

The septic system has three parts: the sewage collection system, which consists of the household plumbing system; the septic tank, which is used for solids retention and biodegradation; and the drainfield, which treats and disposes of the liquid effluent from the septic tank.

The drainfield is the key to this system, according to Scherer. In the course of a year, the drainfield has to treat and dispose of a column of water more than 50 feet high for every square foot of drainfield.

Additives can be separated into three basic types: organic solvents (often chlorinated compounds), inorganic additives (acids, bases and flocculating agents) and biological additives (bacteria, yeast and enzymes).

Biologically based formulations are the most common type. The one most people are familiar with is yeast. Adding a cake of yeast to the septic system is supposed to keep the septic tank working, but research during the last 80 years shows yeast does not make the septic system work any better, Scherer says.

Products containing bacteria and enzymes are based on the idea that many household cleaning solvents reduce the effectiveness of the natural bacteria in the septic system, and therefore they need to be regenerated. However, research shows flushing more than 1 gallon of bleach, 2 pints of a liquid disinfectant or several teaspoons of a drain cleaner down the drain each week does not have much effect on normal bacterial action, Scherer says.

Adding solvent cleaners for organic materials may be effective in removing grease from the household plumbing system and septic tank, but research shows these compounds can end up in the groundwater in sufficient quantities to be harmful, he says. Adding acids and inorganic compounds can cause sludge bulking and disrupt normal biological activity in the septic tank. Plus, using strong bases can be very damaging to the drainfield’s soil structure.

In many cases, septic system problems are the result of an overloaded drainfield. However, research has not found any product that can completely restore a plugged drainfield, Scherer says. He recommends reducing the amount of water going into the drainfield from inside and outside the house to solve these infrequent problems.

Homeowners should direct rain water from roof gutters and outflow from the sump pump away from the septic tank and drainfield, and landscape the area around the septic tank and drainfield to direct surface water away from them. Also, the tile drainage system around the foundation of the house should not empty into the sewer pipe leading to the septic system.

Scherer has this advice on how to reduce water usage in the house:

  • Use low-flow faucets, water-saving showerheads and toilets that use little water.
  • Reduce shower times and use appropriate-sized wash loads.
  • Repair leaky faucets and toilets.
  • Don’t let the water run while shaving, washing hands, brushing teeth or washing dishes.
  • Wash clothes twice a week rather than once to help avoid overloading the drainfield.
  • Reduce the amount of water needed to flush old-style toilets by adding a jug (1- or 1 1/2-gallon plastic milk container) to the toilet tank. Make sure the jug does not interfere with the flushing mechanism.

“If you do put additives into your septic system, read the directions very carefully,” Scherer advises. “Make sure the additive is recommended for the problem you have noticed. However, knowing how your septic system operates, having the septic tank pumped every two to three years and using common sense, along with proper water use, will go a long way toward keeping your septic system operating as it should. At best, septic system additives will only provide a very short respite from problems, and at worst, can increase drainfield plugging, as well as pollute the groundwater.”


Source: Tom Scherer, (701) 231-7239,
Editor: Ellen Crawford, (701) 231-5391,



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