Key Toxins to Keep Out of Septic Systems

Tell your customers to avoid these 5 cleaning products to keep their onsite system working

Key Toxins to Keep Out of Septic Systems

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There are many products your customers use in their homes and commercial properties that can harm the bacteria in a septic system. Below are five key ones to tell them to avoid in order to keep the bacterial community as healthy as possible.

1. Quaternary ammonia – Quat compounds are exceptionally chemically stable water-soluble organic salts, and the chemical bonds are difficult to break so they have a long biocidal effect. The problem is that quats can be toxic to the microbes in our septic systems and in the soil. There are literally hundreds of quats in existence and in common use in home, commercial and industrial products. A review of the ingredients of many products will reveal their presence ( The use of quats should be avoided. For in-home use, natural cleaners such as baking soda, vinegar and borax are preferred along with limited amounts of chlorine and/or other biodegradable cleaners. In commercial kitchens, oxidative sanitizers like bleach or iodine are recommended over quaternary ammonia. 

2. Antibacterial soaps – The use of antibacterial or disinfectant products in the home can and does destroy both good and bad bacteria in the treatment system. Antibacterial products are not needed. A recent study found no difference in infectious disease rates in 228 households that used antibacterial items (hand-washing soaps, cleaners, laundry detergents) versus those that used regular products. In addition, several studies have suggested that triclosan — an ingredient used in many antibacterial items — may breed resistance to germs. Natural cleaners and small amount of bar soap are preferred.

3. Toilet bowl cleaners – Many commercial toilet-bowl cleaners contain bleach and some even use hydrochloric acid. While the acid does effectively dissolve the calcium carbonate deposits in the water, it is also a harmful chemical that will kill off the bacteria in your septic system. Every-flush toilet sanitizers should also be avoided. If cleaned regularly, a brush will keep the toilet clean. The best toilet cleaners for septic tanks are ones made from natural and plant-based ingredients since they are biodegradable and use cleaning agents that easily break down such as baking soda, vinegar and/or borax.

4. Drain cleaners – Drain cleaners work by dissolving the clog with harsh chemicals, but they can also kill the good enzymes and bacteria in the septic tank that help to break waste down and can be damaging to the tank itself. If the plug is in the elbow under the sink, taking apart the plumbing and cleaning it out will typically solve the problem. If not, first try plunging, hot water or baking soda and vinegar. Finally, a snake may be needed if the plug persists.

5. Bleach – Bleach works to keep white clothing white, but if overused, it can wreak havoc on septic tanks. Small amounts of these chemicals, such as the amount when washing one load of laundry, shouldn't be too harmful. However, using color-safe bleach in every load or overusing bleach across a home can cause serious damage to the bacteria in your tank. Avoid running multiple white loads back to back. Whenever possible, do not use bleach. Alternatively, baking soda is great for breaking down stains in the laundry.

Many chemicals can damage septic system bacteria. When customers are looking for alternative cleaners, a great resource is the Environmental Working Group website where they give varying products a grade of “A to F” based on their impact to public health and the environment. 

About the author
Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation, and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association and the National Onsite Wastewater Recycling Association, and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system maintenance and operation by sending an email to


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