What to Pour in Toilet to Make More Bacteria for Septic Tanks?

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Septic systems function best when using the natural bacteria of human waste to break down solids and pass liquids through the system. If a septic system is properly maintained and appropriate to its household usage, there is no need for commercial additives of any kind. In fact, some additives can do much more harm than good.

How it Works

To understand why it’s best to let nature work its own magic, you first need to have a sense of a how a septic system works, how it is best maintained and exactly what the purpose of those bacteria are. Septic systems begin with sewage lines that run from a home’s plumbing system. Starting at indoor sinks, showers, tubs, toilets and other drains, liquids and solids produced in your household pass into pipes, through baffling and into the septic tank. The watertight, underground tank is the holding area for solids – sludge – which sink to the tank’s bottom, and temporarily for liquids – effluent – which are pushed through the system’s pipes and into distribution boxes. From the distribution boxes, the effluent is sent to a leaching field where it is eventually absorbed into the ground environment.

Bacteria in Action

The bacteria in your septic system are microscopic, single-celled organisms that quickly reproduce and work to break down the organic solids originating in your household. Billions of bacteria begin their decomposition work as soon as wastewater enters the system, breaking down complex molecules into simple ones. They are constantly dividing and multiplying, diligently working to consume up to 50 percent of a tank’s sludge and turn it into gas and liquid matter.

Replacing Bacteria

Because nonorganic cleaning chemicals can have an adverse effect on septic systems, homeowners sometimes mistakenly believe that they need to do something drastic to counter those effects. In reality, it would take very large quantities of any adverse substance to destroy the billions of bacteria which have had time to breed in your septic system. Additionally, bacteria can be naturally replaced with the simple activities of your household – flushing the toilet being top among them.

False Claims

There are many products that promise to increase bacteria production in your septic system and thus reduce solid materials and the need for frequently pumping the tank. The problem with their claims is twofold: added bacteria are unnecessary and pumping the tank is vital to the proper maintenance of your system.


Well-designed and maintained household septic tanks generally have enough space for three to five years of accumulated sludge. However, contributing factors, such as the number of residents, tank size, the presence of a garbage disposal or the disposal of non-tissue products into the plumbing, can cause the system to require more frequent pumping. As a rule, a family of four, using a tank size of 1,000 to 1,250 gallons, should have its tank pumped once every three years.