The paint: your septic tank worst enemy

Category: Home
13 Jan 2023

What do you do with your brush after you are done painting? Well, the answer shouldn’t be washing it in your sink. Doing so could ruin your septic tank. Here is the explanation:

Paint is made up of four components namely, a solvent, a binder a pigment and additives.

AdditivesThe main role of additives in paint is to kill algae, fungi, and mold but they are also used as fillers.

BinderThe role of the binder is to ensure the paint holds in place. In so doing, it helps to protect the surface from being damaged by the elements. The binder in paint is usually made from a polymer.

PigmentThis is what gives the paint the color.

SolventsThe solvent is the part of the part that usually dries and it is either some form of hydrocarbon (oil) or water.

Suffice it to say that paint and septic tanks do not mix and you should therefore only buy paint that will be enough so that you use it up completely. If you have some leftover paint, dispose of it at the nearest toxic waste disposal center.

The effects of mixing paint and septic tanks

Sludge buildup

The septic system is designed to treat wastewater through a combination of physical and biological processes. As the bacteria and enzymes break down the organic waste, other suspended solids sink to the bottom of the tank to form the sludge layer. Since paint cannot be digested by bacteria, sending it to the septic tank means it will accumulate in the sludge layer and that can result in the septic tank filling up faster than usual.

Blockage and backups

Lots of chemicals are used in the making of the binder part of paint. The binder helps the paint to hold in place while protecting the painted surface from abrasion or moisture. Solvents usually evaporate but the binder forms a layer that will “bind” the paint. For most modern paints, the binder is made from a polymer (plastic). If this paint gets sent down the drain, the binder might stick to the surfaces of the pipes in the plumbing, the septic tank or even in the drain field. This can lead to blockages in the pipes and this can be a serious problem especially if this blockage happens in the drain field area.

Killing helpful bacteria

Most of the components of paint are toxic to bacteria. For instance, the main purpose of the additives is to kill microorganisms like bacteria and fungi. The same is true for the plastics found in the binder. Additionally, Lead and other heavy metals are also commonly used in paints for pigmentation and these piments are also toxic to microorganisms. Clearly, paint poses a huge risk to bacteria and should therefore not be allowed to get into the septic system.

Contamination of water

If paint finds its way into the septic tank, there is a good chance that it will end up in the drain field. This is because paint cannot be digested by bacteria. Instead, it might mix up with the effluent and percolate in the drain field area. This will result in pollution of either groundwater, drinking well water, or both. The law is very strict and if your system pollutes the environment like this, you might end up paying a dear price for the totally avoidable mistake.


Paint and septic tanks – cleaning up after painting

Before you start painting the house, think about how you will dispose of the leftover paint and the cleaning that will be needed. Your goal should be to avoid getting paint into the septic system. Knowing this from the very onset will help you to plan your painting project better. For instance, you can use disposable paint rollers and brushes. This will save you the trouble of having to clean once the job is done. Another importance of planning your work in advance is that you will only buy the paint you need for the job. Your goal will be to use up all the paint in order to avoid having to deal with disposal.

However, it is unlikely that you will complete the painting without any leftover paint. In such a scenario, pack up the paint with the roller and brushes and take it to the nearest hazardous waste facility where it will be disposed of properly. Washing the brushes in the sink will expose helpful bacteria to the toxic substances in the paint so do not attempt to do it. Remember to use gloves when handling the paint so that you do not have to wash off any paint in your sink.

Remedy if paint gets into the septic system

We have demonstrated the importance of keeping paint away from the septic system. Nonetheless, you might find yourself in a situation where paint inevitably gets into the septic system.  The steps you take after this depends on how much paint got into the system. If the amount of paint is negligible, like say the paint came from washing your hands, it shouldn’t be that big of a deal. However, if too much paint was poured down the drain, then you might want to take more drastic measures like scheduling to pump the tank and doing shock treatment after the tank has been completely emptied.  Shock treatment is the introduction of biological additives into the septic tank either by flushing them in the toilet or by pouring them directly into the septic tank. The additives will add billions of bacteria and enzymes into the system and this will help the septic tank to recover from the shock of the toxic substances that were introduced by the paint.


When seated on your walls, the paint might look harmless but the havoc it can wreak in your septic system is of epic proportions. As a septic system owner, it is your responsibility to do whatever it takes to prevent paint from getting into the septic system. Not only will the paint harm the bacteria in the septic tank but it could potentially pollute the groundwater. In other words, think about the disposal of your paint leftovers before you embark on your DIY project. If you are still in doubt, you are better off hiring a skilled contractor who understands paint and septic tank management to help you with it.

About the author


CEO at Bio-Sol

Our goal is not only to offer you the best products on the market but also to educate and empower you with the insights you need for successful wastewater treatment.


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