What Are Septic Tank Additives and Do You Need Them?

Candace Nelson
Written by Candace Nelson
Updated September 30, 2021
A family spending time at front porch of their rural home
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Septic tank additives are unnecessary when you properly maintain the system

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Septic tanks are designed to take care of waste disposal on their own — no additives needed. With regular septic tank pumping and inspections, a septic system should last decades. 

A septic system is used primarily in rural areas without access to city sewer systems. To understand why a septic system does not need additives, it helps to first understand how a septic tank works.

How Septic Tank Systems Work

The septic tank is essentially a holding tank that provides the first step in the treatment process for solids and wastewater coming from the home.

A main job of the septic tank is to keep solids, grease, and oils from entering your drainfield. The drainfield is a shallow area where the pretreated wastewater filters through soil.

When wastewater enters the tank, it breaks into three layers. The first layer is a fat or grease layer, the middle layer is clear wastewater known as effluent, and the bottom layer is solid waste.

Bacteria that live in the septic tank help break up the solids down to liquids or gas. Some solids like sand or little toy cars that got flushed will not get broken down. Those settle to the bottom and require the system to be pumped every three to five years (more often if you have a household member who routinely flushes things they shouldn’t) to keep the system from backing up.

But those mighty bacteria will break down organic solids—as long as they are given an environment to thrive in.

What Septic Tank Additives Do

A man using gloves opening a septic tank
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The bacteria in the septic tank are key to the system working. Without it, those oils, fats, and organic solids wouldn’t get broken down. The septic system is perfectly designed to work with very little interference from you. So don’t fall for septic system myths. You don’t need to spend $15 per bottle to put additives into the system. In fact, don’t.

Any additives, including drain cleaners, disinfectants or bleach, can kill off all of the healthy bacteria in the tank and put the septic system in jeopardy. A University of Arkansas at Little Rock study found that water softeners not only killed microorganisms in the tank but also interfered with solids settling in the tank, putting the system at greater risk of failure. 

Some additives are advertised to help control the smell of formaldehyde, quaternary ammonium and zinc sulfate, but in the process, they poison the system and its bacteria. Ultimately the store-bought cleaner can lead to expensive damage. Septic tank additives have caused enough system failures that some states have banned them. 

In addition to harming the bacteria that efficiently handles a pretty gross job, septic tank additives can also corrode the tank itself and the pipes. If you notice a new septic system smell, a local septic tank expert can help diagnose and treat the problem. If you go out to investigate what’s wrong with the septic system, be sure to practice septic tank safety.

How to Care for Septic System Bacteria

It’s not just commercial additives that can kill septic system bacteria. Keep those bacteria healthy and working by:

  • Properly diluting cleaning solutions because cleaners that end up in the drain can kill bacteria.

  • Keeping toxins like leftover stain, paint, and oil out of the sink. Check your county or city’s waste management site to learn how to properly dispose of it.

  • Spacing out water use. Wash clothes on multiple days of the week, for example, to avoid overloading the system on one big wash day.

How to Maintain Your Septic System

A septic system isn’t meant to be bacteria-free and rain-fresh scented. No septic tank additive will work better than a septic tank’s natural function and use of healthy bacteria. The best thing you can do is let the bacteria work and do your regular septic tank pumping and inspections. In fact, some additives can harm the system and cause septic system failure, which will then require replacement.

The Environmental Protection Agency recommends some septic system best practices, in addition to regular inspections and pumping, to protect your septic system.

  • Conserve water: Use high-efficiency showerheads and toilets. Wash full loads of laundry or use the small load setting.

  • Properly dispose of waste: Everything you flush or send down the drain ends up in the septic system. Things like feminine hygiene products, dental floss, and diapers should be thrown in the trash. Chemicals like paints and cleaners should be properly recycled as they can kill the septic system bacteria. 

  • Maintain your drainfield: Know where your drainfield is and don’t park cars on it. Landscape around a sewer system a safe distance away to prevent system disruption. Guide rainwater away from the drainfield and don’t drain items like pools over the drainfield. Adding water to that area can cause system slowdown.

If you have a question about a certain additive or want more information, call your state government office that regulates wastewater and septic systems.

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