What Causes Sinks to Smell Like Sewer When You Are on a Septic System?

Homes constructed in areas of the country where there is no municipal sewer system will often have a septic tank, which collects and treats a home’s waste water. If something is wrong with the septic tank, a sewer-like smell may occur in your sinks, drains, toilets and even in your water supply. Depending on the cause, this smell can result in dangerous bacteria in your water supply.


A sewer smell in your sinks can indicate a serious problem.

Septic tanks use beneficial bacteria to disinfect and treat waste water from your home and prevent it from contaminating groundwater, well water and local bodies of water. A properly functioning septic system should never cause smells around the septic tank or in the home, but a sewer smell in your kitchen sink is a sign that something is wrong.

Full Tank

Septic tanks usually need to be emptied by a professional every three years if they are properly maintained. A sign that your septic tank is full is a wet, soggy and smelly lawn in the area of your yard where the septic tank is located. If the septic tank is full, it can be leaking into well water or the waste water in your home, causing a sewer smell. It should be emptied as soon as possible.


Septic tanks normally have a lifespan of about 25 years if they are properly maintained. If your septic tank is older or in disrepair, it may rupture or leak, contaminating well water or groundwater and resulting in a sewer smell in your drains and water supply. If you do have a sewer smell in your home and are on a septic tank, you should have the septic tank inspected as soon as possible.


Even though a home is on a septic system, the sewer smell coming from drains and the water itself can be related to an entirely different problem. A rotten or sewage smell in drains can be caused by bacteria growth, and this bacteria grows on organic matter that goes down the drain, such as food, hair and soap. The easiest way to determine where the smell is coming from is to fill a glass of water and smell it. If the water itself smells, there may be bacteria growing in the hot water heater or a septic tank issue. If the drain smells, the drain can be disinfected with drain cleaner or bleach.