House Grail is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Why Does My House Smell Like Sewer: 9 Possible Reasons

living room with air conditioning

There are few things worse than walking into the kitchen, bathroom, or any room of the house, really, to get a whiff of the unmistakable scent of sewer. It’s unpleasant, it’s worrying, and it’s actually quite unhealthy. What’s more, it could be a sign that something is seriously wrong and needs attention quickly. If your house smells like sewage, you first need to identify the cause, before you can take action to remedy the problem.

Below are 9 possible reasons for the stink, as well as a guide on what you will need to do to fix things.

divider 4 Why Does My House Smell Like Sewer (9 Possible Reasons)

1. Biofilm In The Shower

Biofilm is a collection of bacteria, of different kinds, and can be found around the tub, in toilet bowls, and on tiles and sinks in the bathroom, but are also often found in the shower cubicle. The biofilm will usually have a pink tinge, which is an indication that it contains the bacteria Serratia marcescens. The bacteria not only adheres to other bacteria but sticks quite firmly to the surface it resides on.

There are many cleaning products that can help get rid of this particular collection of bacteria, but baking soda is also effective. It will take some work, and once you’ve scrubbed the sticky mess away, you should ensure that you keep the area clean afterwards through regular cleaning with a good quality cleaner.

curved shower door_Deyan Stoev_shutterstock
Image Credit: Deyan Stoev, Shutterstock

2. Dry Shower Trap

The shower trap takes waste water out of the shower and transports it to the drain. It is installed in a watertight area under the shower unit that is designed to prevent smells from getting into the bathroom. As water regularly runs down the trap, this prevents smells from getting back up and out of the sewer. However, if the shower has not been used in some time, it can dry up and this allows smells to back up. It is also possible that bacteria has started to reside down there.

Generally, the fix for a dry p-trap is thankfully simple. Run or pour some water down there and it will get rid of the smell. You can also tip some white vinegar bleach in to help get rid of particularly nasty smells.

3. Vent Pipe Was Installed Incorrectly

A vent pipe, or vent stack, allows air to be properly expelled from the plumping system. The pipe is usually I the crawlspace and colored black. If it has been installed incorrectly or become damaged, it won’t allow potentially odorous gases out of the toilet system and they may find their way back into the room.

Unfortunately, this will usually require a professional plumber. They will be able to quickly identify this problem and either repair the existing pipe or fit a new one.

Image Credit: Christian Horz, Shutterstock

4. A Broken Toilet Seal

Toilets are obviously a fairly common cause of bad smells, but they are designed to help get rid of those smells efficiently and safely. To help prevent smells and dirty water from getting out of the system, the toilet is usually sealed in at least two places. If the seal breaks, sewer gases and smells can escape. A broken seal may also mean that the toilet bowl does not fill properly when flushed.

Locate the seals and see if there are any obvious signs that they are broken. Apply caulk to the wax seals and the bolts around the toilet.

5. The Sink Overflow Is Clogged

Sinks come with an overflow near the top. If the sink fills too high and runs the risk of overflowing onto the floor, the water escapes through the overflow and out through the wastewater system. If, at some point, dirty water has passed through the overflow and then been allowed to dry or dirt and debris in the water has gathered in the overflow, it could have caused a bacteria build-up that results in a bad smell around the sink.

You can get special cleaning snakes to help with the job, but a bottle brush is sufficient. Use a diluted bleach solution and some water and clean out the overflow to get rid of the smell.

stainless steel sink-pixabay
Image Credit: balog, Pixabay

6. Clogged Washing Machine Drain

Where there is a drain, there is the potential for a clogged drain, and this is true with washing machine drains. Once the pipe gets clogged, it will allow detergent, soap, and dirt and grime to build. Eventually, this will cause odors around the washing machine area and it may even cause your clothes to smell once they’ve been through the washing machine.

In this case, you probably will need the drain snake to enable you to reach right into the drain. Use the snake to budge the build-up and the smell will soon follow.

7. Bacteria In The Water Heater

If you don’t use hot water for some time, or if you only ever run warm water through the water heating system, it can allow bacteria to develop and multiply. This can cause a sulfur smell that smells bad but shouldn’t do any harm to you or others in the house.

Turn up the water temperature and run the hot water taps. This should kill off the bacteria. If the smell hasn’t improved after 24 hours, it could be something else or the water heater might need further attention.

hand rotate temperature adjuster of water heater_cunaplus_shutterstock
Image Credit: cunaplus, Shutterstock

8. Decomposing Waste

Sometimes, a sewer smell can be caused by the sewer itself. If the smell is really strong, it can ruminate from the sewer and pass into the house. This most often happens when there is a build-up of waste that is allowed to decompose and break down.

You’re going to need to clean the sewer system, which is not a pleasant job and if you’re not comfortable getting sewer cleaning rods out yourself, get a professional company to come and do it for you.

9. Clogged Drains

There are drains pretty much everywhere around your house. They come from the sinks, the bath, the shower, and even from the heating and hot water systems. Unfortunately, they can become clogged, typically with a combination of hair, soap, and dirt. Over time, bacteria builds up and eventually causes a really unpleasant smell.

Identify the drain that is causing the smell and either unblock it or try using a diluted bleach solution to help break down the blockage and kill off the bacteria.

divider 7 Conclusion

A sewer smell is an especially unwanted guest in your home, and there are many possible causes. Try to determine where the smell is coming from, look for any obvious signs of blockage, damaged pipes, or water build-up. If you can’t fix the problem yourself, it is time to call a plumber, because sewage gases can actually be quite harmful to you, your family, and your pets, especially if they are left to worsen.

Featured Image Credit: 3DPhoto, Shutterstock


Related posts

OUR categories

Project ideas

Hand & power tools