Reasons Why You Smell Sewage in Your Home

A foul odor in your home can be more than just a minor annoyance—it might indicate a serious underlying issue, especially if it smells like sewage. A sewer smell in the house, often compared to rotten eggs or sulfur, can be hazardous to your health and requires immediate attention.
Septic tank smells in areas like your bathroom, kitchen, or laundry room may point to more than just a simple plumbing backup. The problem could stem from the sewer itself, necessitating prompt action. In some cases, the solution might be straightforward, such as running water to refill a dried-out P-trap. However, professional intervention may be required if the issue involves a broken vent pipe.

Unusual sewage smells in your house should always be addressed. Finding the source, however, can be challenging, as the odor might originate from various places within your home’s plumbing system, including the shower or toilet.

Learn how to identify the source of sewage odors in your home and troubleshooting steps to resolve the issue. However, only a professional can address the problem in some cases.

What Does Sewer Gas Smell Like?

Sewer gas has a distinct, unpleasant odor, often resembling the smell of rotten eggs. This odor is due to hydrogen sulfide, which forms due to natural human waste breaking down. To locate the source of the sewer smell in your home, follow your nose to where the odor is strongest. Some common sources include:

1. Dry P-Trap

If your house smells like sewage, your first step is to locate the source of the odor. If the smell is coming from a specific sink, such as in the kitchen or bathroom, a dry P-trap could be the culprit.

The P-trap, a U-shaped pipe found under every sink, connects your sinks to the plumbing system. It holds a small amount of water that acts as a seal, preventing sewage odors from rising through the pipes and entering your home. If the P-trap dries out, this seal is lost, allowing odors to escape.

Fortunately, fixing a dry P-trap is simple. Run water down the drain for 1 to 2 minutes to restore the odor-blocking seal. However, if the P-trap keeps drying out or the foul odors persist, it could indicate a more serious issue, such as a cracked sewer line or septic problem, requiring professional attention.

2. Clogged Vent Pipes

If you notice a sewer gas smell in the house but can’t tell where it comes from, the vent pipes might be obstructed. These pipes allow air into the plumbing system to maintain proper pressure and safely vent sewer gases out of your home.

Vent pipes typically extend to the roof, where they can sometimes become clogged with leaves, twigs, or bird nests. When this happens, the gases that should be vented out can get trapped and seep back into your home.

To clear a clogged vent pipe, remove any visible debris from the openings, then use a garden hose to flush out any remaining obstructions. If you can’t clear the vent pipe yourself or if the odors persist, it’s best to contact a professional technician.

3. Broken or Damaged Sewer Line

Does the sewage smell in the house come and go, varying in intensity over the day? This could indicate a cracked or loose sewer line. A damaged sewer line intermittently releases sewage gases, causing the odor to fluctuate. You might notice the smell more when water is running through your pipes or during heavy rain.

Inspect your sewer lines for any signs of damage. If you find cracks, leaks, or broken sections, it’s a serious issue that requires immediate attention. Call a plumber right away to prevent further problems.

4. Cracked Toilet Base

If your house smells like sewage and the odor originates from your bathroom, it’s a good idea to check the base of your toilet bowl for gaps or cracks. Even if the rest of your plumbing is in good shape, these can let odors leak into your home.

Cracks in the toilet base can occur due to poor installation, wear and tear, or sudden temperature changes. Besides the bad smells, monitor for other signs like:

• Large cracks near the toilet base
• Water pooling or wet floor near the toilet
• Stains or discolorations on the floor
• Signs of mold or mildew growth around the toilet base

If you detect any of these signs in addition to foul odors, the wax seal ring under your toilet base may have failed. Stop using the toilet immediately and contact a professional plumbing technician to repair or replace the seal.

5. Biofilm Build-up in Drains

Foul odors in the home are bad news, but they aren’t always sewage gases. In some cases, they come from build-ups of what professionals call biofilm.

A biofilm is a slime-like layer of bacteria. They grow on the inside of water pipelines, attracted by stagnating water and organic waste, such as hair, soap scum, grease, or food particles. This slime produces a foul odor.

The more the biofilm grows, the more it absorbs oxygen, producing other toxic and foul-smelling gases like methane or sulfide. These gases intensify the sewage-like smell, increase the risk of corrosion in your home’s plumbing, and are hazardous to your health.

You can tell if you have biofilm build-up in drains from sewage issues by looking for these signs:

• Type of odor. Biofilm odors are damp and closer to mold and mildew. They are noticeably different from sewage, which smells like rotten eggs or sulfur.
• Slime on the drains. Inspect the edges of your drains. Biofilm often leaves clear, white, or grayish substances with a sticky or gooey texture.
• Odor location. Biofilm generally builds up only in one drain or pipe at a time. If only one drain produces the foul odors, you may have a biofilm problem instead of a more generalized plumbing issue.
• Stronger after using the fixture. They become stronger and more noticeable after using an affected bathtub, sink, or shower. The flow of water disturbs the biofilm’s surface, causing it to release gases and odors.

After identifying the signs of a biofilm growth inside one of your drains, try pouring boiling water to break it down and flush it down the pipes. You can also try enzyme-based cleaners or a solution of baking soda and vinegar, then pour boiling water down the affected drain again. If none of the DIY methods helped, call a plumbing technician to inspect and thoroughly clean your piping system.

6. Overflowing Septic Tank

If you’re wondering, “Why does my house smell like a sewer?” and you have a septic tank, It should be the first place you check—it may be full and overflowing! When a septic tank is too full, there’s no room for sewage and wastewater, so odorous gases can back up into your house. Some common signs that your septic tank might be overflowing:

• Unusually lush or green grass over the drain field (the wastewater is a potent fertilizer)
• Foul odors coming from the septic tank or the drain field
• Gurgling noises from the drains and toilets
• Slow drains or non-functional toilets
• Unusual plants or algae growths near the drain field

If your septic tank is full, the first thing to do is call your septic service provider and schedule a tank pumping. While waiting, try to use less water and limit bathroom usage to avoid worsening the problem. It’s also a good idea to check your pipes, tank, sump pump, and drain field for any signs of damage. An overflowing tank can strain your septic system, and you might need a professional plumber for repairs.

Contact a Professional Plumber

Simple DIY fixes can often eliminate sewage odors in your home. However, if the issue feels too complex or you’re not confident handling it yourself, call a professional plumber. They can resolve the problem and provide guidance to prevent future issues.