© kaliantye / Adobe Stock

Because your septic system is such a critical part of your home, it’s natural to want to do whatever you can to keep it running reliably.

Manufacturers of septic tank additives know this and offer products that promise to reduce the need for pumping, dissolve clogs or otherwise improve your septic system. 

In reality, though, these additives aren’t necessary and often do more harm than good.

Before you decide to add anything to your septic tank, get to know how these systems and the most common additives work.

    How Septic Systems Work Without Additives

    The biggest reason so many people use unnecessary or harmful septic tank additives is that they don’t really understand how a septic system does its job. Septic systems work by taking advantage of a completely natural biological process that doesn’t need any human intervention. They’re designed to work without additives.

    Your septic tank receives all the wastewater and waste solids from your home’s plumbing system. This waste contains bacteria that, once in the septic tank, separate the waste into layers. Solids fall to the bottom creating a layer known as sludge, while fats rise to the top to create a scum layer.

    In the middle is a layer of clear wastewater called effluent. In most systems, the effluent flows through devices that further purify it and gradually release it into the soil.

    The natural bacteria in the tank get all the nutrients they need from the waste that’s already there with them. You don’t need to add more, feed them or support them at all. If you add more bacteria without more waste, the bacteria will only eat each other. The bacteria are anaerobic, so they don’t even need air.

    All your tank needs to stay in shape is regular inspection and pumping to remove the solid sludge layer. No additive can break down this layer to delay or replace pumping.

    Today’s Homeowner Tips

    Inspect the system or have it professionally inspected every one to three years, depending on the system type. Have the tank pumped to remove solid waste every two to five years depending on your household size, how often you use the tank, and your climate.

    The False Promise of Septic Tank Additives

    Manufacturers of septic tank additives typically claim their products help break down the solid waste layer or the scum layer so you won’t need to have your tank pumped as often. Other products promised to restore a clogged soil absorption system.

    Additives come in two types:

    These are bacteria, yeast, and enzyme products manufacturers sell as a way to start a new septic system or support an overworked system. Because the system gets all the bacteria it needs from the incoming waste, though, biological additives are unnecessary. They won’t harm your system, but they don’t help, either.

    If your system really is overworked, you either need to cut back on your water use or have the tank pumped more often. In some cases, the system might have been designed or installed incorrectly and will have to be overhauled.

    This group includes organic and inorganic products formulated to break down the sludge or scum layer, control odor or restore a clogged drainfield. Household drain cleaners and degreasers fall into this category. These are more dangerous than biological additives because they often upset the pH balance in the tank enough to kill the bacteria the tank needs to run properly.

    The ones that actually do what they promise interfere with the waste separation process. For example, by dissolving the scum layer, they can cause scum to seep into your soil and groundwater. At worst, they can damage the system’s pipes and other components.

    Gentler household products, such as hydrogen peroxide, won’t harm the bacteria much, but can still contaminate the drainfield’s soil, reducing its ability to purify wastewater.

    If you notice a foul odor or pooling water around the drainfield or your drains are running slowly, your septic tank needs to be pumped. No additive will solve these problems.  

    Managing Special Situations

    Some septic tank additives are marketed for use in unusual situations, but even in these cases, there’s little an additive can do.

    In a vacation home where the septic system goes unused for months at a time, the bacteria load can drop so low the system isn’t as efficient as it would normally be. To solve this problem, save any heavy water-use activities, such as running the dishwasher or doing laundry, for after the toilet has been used a few times to add more bacteria.

    Some septic service providers include bacterial treatments for infrequently used systems as part of their cleaning and inspection services, but beware of anyone pushing you to buy separate additive products.

    Today’s Homeowner Tips

    If your septic system hasn’t been used for several years, have it professionally inspected before you start using it.

    As long as the tank isn’t damaged and the pipes haven’t accumulated dirt, though, the system should be just fine. If there is damage or dirt, you’ll need professional repair work or cleaning. Additives won’t help.

    Hosting a full house of guests for a few weeks can strain your septic system. To protect the system, you can ask your guests to limit their water use, but you don’t need to add a bacteria product.

    With all the septic tank additives on the market, it’s tempting to think at least a few of them might help your system run more efficiently. In reality, biological additives are largely a waste of money, and chemical additives can harm the system.

    The best thing you can do for your septic system is to let it work as designed with only natural bacteria. Beyond that, have it pumped and inspected regularly, and it will perform well for decades.

    Editorial Contributors
    avatar for Henry Parker

    Henry Parker

    Henry Parker is a home improvement enthusiast who loves to share his passion and expertise with others. He writes on a variety of topics, such as painting, flooring, windows, and lawn care, to help homeowners make informed decisions and achieve their desired results. Henry strives to write high quality guides and reviews that are easy to understand and practical to follow. Whether you are looking for the best electric riding lawn mower, the easiest way to remove paint from flooring, or the signs of a bad tile job, Henry has you covered with his insightful and honest articles. Henry lives in Florida with his wife and two kids, and enjoys spending his free time on DIY projects around the house. You can find some of his work on Today’s Homeowner, where he is a regular contributor.

    Learn More

    Top Plumbing Companies Near You