Are septic tank additives good or bad?

Man in overalls opening green septic tank lid with protective gloves.

Septic tank additives are commonly marketed to homeowners, but the lack of regulation, standardized testing, and formal certification for these products has led to confusion about how well they work – and whether they are needed at all.

As external observers (we do not sell septic tank additives), our goal is to share the facts for the different types of products available so that you can make an informed decision about the best maintenance strategy for your septic system.

What are septic tank additives?

Man shopping in supermarket reading product information.

In general, septic tank additives are designed to improve the performance of septic tanks or leach fields (also known as septic drain fields). Additives can be divided into three categories: inorganic compounds, organic solvents, and biological additives.

Inorganic compounds

Inorganic compounds, such as strong acids and alkalis, are marketed as a way of unclogging septic system pipes. While these products may work as advertised, we suggest you avoid them because they:

  • corrode and cause leaks in concrete treatment tanks
  • stop the anaerobic digestion process in septic tanks
  • kill bacteria that are essential to the wastewater treatment process
  • reduce the effectiveness of conventional septic systems
  • disrupt the performance of secondary treatment systems (including Ecoflo biofilters)
Organic solvents

Organic solvents are designed to break down fats, oils, and greases in septic systems. Again, even though these products may achieve their stated goal, we suggest you avoid them because they:

  • kill essential bacteria in septic tanks
  • negatively affect the health of conventional septic systems
  • impair the performance of secondary treatment systems
  • contaminate groundwater
Biological additives

Biological additives, such as yeasts, bacteria, and enzymes, are intended to improve the bacterial flora in septic tanks and leach fields, control biomass in septic tanks, or reactivate “dead” or dormant septic systems.

This category of septic tank additives is perhaps the most common on the market, so let’s look at it in more detail.

Types of biological additives for septic systems

Person dropping a biological septic tank additive with bacteria and enzymes into their toilet.

Biological septic tank additives can be divided into two main groups: those that are formulated with bacteria and those that are formulated with enzymes.

Do I need to add bacteria to my septic tank?

Bacteria-based additives are designed to restore and support bacterial growth and activity in septic tanks.

Healthy septic systems already contain enough bacteria to support the biological processes necessary for wastewater treatment. By adding more bacteria to your septic tank, you create conditions in which bacterial populations compete against each other. Ultimately, this competition can reduce, rather than increase, the effectiveness of your septic system.

The same principle holds true for yeast-based additives, which are meant to break down starches in your septic tank. Because starches represent only a small percentage of the organic contaminants in your tank, an influx of yeast may leave little room for bacteria that break down more numerous compounds, such as proteins, fats, fibres, and pectin.

Unhealthy septic systems are a different story. Often, the bacterial flora in these systems has been destabilized by large quantities of toxic substances, including:

  • antibacterial soaps
  • disinfectants and other cleaning products
  • pharmaceuticals
  • pesticides

In this case, when populations of bacteria are too small to support effective wastewater treatment, septic tank additives may be an option to re-establish a healthy balance in your septic system.

To determine if this step is right for you, we strongly encourage you to contact your septic system manufacturer or ask our team of experts for advice.

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Do I need to add septic tank enzymes?

Enzyme-based additives are meant to stimulate bacterial populations in septic tanks. They do this by simplifying the structure of the organic contaminants the bacteria feed upon.

There are two important things to know about septic tank enzymes:

  1. They are specific. For example, take two commonly marketed enzymes: cellulase and protease. Cellulase solubilizes only fibrous materials, such as toilet paper, and protease solubilizes only protein-based pollutants. For all other organic contaminants, these enzymes are ineffective.
  2. They are not alive and cannot reproduce. Unlike bacteria-based products, enzymes must be regularly purchased and added to your septic system to maintain their intended performance.

Some septic tank enzymes are sold to limit the accumulation of surface scum. They work by allowing fats, oils, and greases to flow downstream into secondary treatment systems and other septic system components.

The problem is that fats, oils, and greases are supposed to stay in your septic tank so that they can be removed by a septic pumper. If they are discharged downstream, they can overload your septic system components, reducing their performance and shortening their lifespan.

The verdict on septic tank additives

Overhead view of a septic technician inspecting the wastewater and pipes in a septic tank.

So, in the final analysis, are septic tank additives good or bad? To decide, we recommend that you draw your conclusions from two sources: the scientific community and the environmental regulations in your area.

What science says about septic tank additives

There is little scientific evidence to suggest that you should add bacteria or enzymes to your septic system.

In fact, several studies have shown that the addition of bacteria or enzymes has no statistical effect on bacterial populations, sludge, scum, or concentrations of total solids (D'Amato et al., 2008; Pradhan et al., 2006, 2011a, 2011b).

These studies are supported by findings from the United States Environmental Protection Agency (EPA), which reported that biological additives do not appear to improve the performance of septic tanks. These same findings were unable to justify the cost of septic tank additives for residential use (EPA, United States, 2002).

Why? In well-maintained and healthy septic systems, concentrations of microorganisms and enzymes in raw wastewater are high enough to support the anaerobic treatment process in the septic tank. The amount of bacteria or enzymes that can be artificially added is negligible compared to populations already present in the biomass.

Septic tank regulations near you

The makers of many septic tank additives claim that their products eliminate the need for septic tank pumping. Treat these claims with skepticism.

Some of the solids sent to your septic tank are non-biodegradable, including minerals, synthetic fibres, plastics, and other debris. No amount of septic tank enzymes or bacteria will break down these materials. They will accumulate in your tank until a septic pumper safely pumps them out.

This is just one of the reasons why most jurisdictions require homeowners to have their septic tank professionally pumped on a regular basis. Buying and using septic tank additives does not exempt you from these regulations.

Your next steps for a healthy septic system

In the end, the best thing you can do for your septic system is to have it properly maintained by a trained professional. For your septic tank, that means close inspections, regular pump-outs of accumulated sludge, and an effluent filter that is cleaned as often as needed.

For fast and free advice about septic services in your area, or any other topic related to your wastewater treatment system, contact our team of experts today. We are always here to help.

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