5 Common Causes of Septic Tank Odor

Becca Stokes
Written by Becca Stokes
Updated September 16, 2021
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Say bye-bye to bad smells

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You probably never really want to think about your septic tank, but when your home starts to smell less-than-fresh, it can be the source of the problem. A regularly serviced septic tank system can last for years, but a bad smell in your home could be a sign of trouble.

What Is a Septic Tank, Anyway?

A septic tank is an underground container where household sewage is treated. Not all homes have septic tanks; in urban areas, homes are connected to the local sewerage systems instead. But in more rural areas where that connection isn’t possible, septic tanks are a good alternative.

So what makes them “septic”? That word refers to the naturally occurring bacteria inside of the tank. It’s this bacteria that is responsible for breaking down the matter inside. 

In a functioning septic system, when new wastewater is flushed down the toilet and enters the tanks, old, treated wastewater is pushed out into a drainage field (made up of underground perforated pipes). That wastewater eventually is absorbed into the ground a safe distance from the house.

If your septic tank isn’t working the way it should, that leads to bad smells. That’s because the bacteria inside your tank makes gas as it breaks down the waste. If this gas can’t be contained because of a problem with your septic tank or how you’re using it, it may create a foul septic tank odor. 

Here are some common reasons why your septic might stink, and what you can do about it.

1. Clogged Drains

If your drains are clogged, they can dry out. And while a dry drain doesn’t sound bad, it can cause problems—like odor! 

When a clog forms, it dries out the pipe, and that means there’s no ventilation that’s essential to combatting odor. Dry drains can’t filter the gases building in the tank. Instead, the gas can seep into the home, causing a bad smell. If you think a clogged drain (or drains) could be part of the problem, contact a plumber in your area to take a look.

2. Ice Build-Up

In particularly cold weather, ice can build up on the vents of your plumbing pipes. A little ice is no biggie, but too much means air can’t move through the vent and the gases from your tank will be redirected into your home. Not very nice.

This problem you can handle by yourself if you are able to remove the ice from the vent easily without causing damage. If you’re worried the situation has gone too far, then it’s time to bring in a professional.

3. Blocked Vents

While ice buildup can cause issues, it isn’t just inclement weather that can lead to blocked vents and the bad smells that follow. Your landscaping, if not maintained, can also block those vents. 

Make sure to regularly trim any bushes that could block the vent, and keep your lawn trimmed, too.

4. Broken Pump

One of the key components of a septic tank system is the pump. The septic pump helps move wastewater in and out of the machine. If your septic tank pump is out of date, it may not be able to meet the demands of capacity required for your household. 

Contact a plumber in your area to assess the situation if you suspect that a broken pump is to blame for odors in your home.

5. Full Tank

While septic tanks naturally treat waste, they can’t keep up with how regularly waste is deposited into the tank. That means you need to have your septic tank regularly emptied. If you don’t, it can back up, leading to bad smells and a potential sewage spill in your own home. 

Make sure you are well-educated about the safety issues every septic tank owner should know and keep up with necessary maintenance. You should have your septic tank inspected every one to three years, and the Environmental Protection Agency suggests that you have your septic tank emptied every three to five years. However, certain factors could mean that you need to do it more frequently, including:

  • Number of people in the house

  • Amount of wastewater generated

  • Volume of solids in wastewater

  • Size of septic tank

The average cost to have your septic tank pumped or cleaned is $410. Most homeowners spend between $290 and $540. Very large tanks can cost $1,000 or more.

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