Why Does My Toilet Smell like a Sewer?

As you enter your bathroom, you wrinkle your nose at the faint sewage odor. Although bathrooms sometimes have odors, this one feels unusual. You move closer to the sink, shower drain, and toilet, trying to find where the sewer smell is coming from. Neither cleaning nor using the fan seems to help. Why does your bathroom smell like sewage?

Unfortunately, various factors can lead to a sewage smell in your bathroom, making it challenging to identify the exact source. Beyond the unpleasant odor, the methane in sewer gas can be flammable in large amounts, posing a health risk if inhaled.

Luckily, once you pinpoint the cause of the issue, eliminating the sewage odor is typically straightforward and cost-effective. Want to restore your fresh-smelling bathroom? Keep reading!

Possible Reasons Your Bathroom Smells Like Sewage

A basic understanding of how the plumbing in your bathroom works can help you pinpoint the issue.

How the P-Trap Works

At some point, you might have looked under the bathroom sink and noticed the U-shaped pipe that connects your sink drain (B) to a larger wastewater pipe in the wall. This pipe is known as the P-trap.

One end of the P-trap goes down to your sewer or septic system (E), while the other end extends up through the roof (D), allowing fresh air in and letting any unpleasant sewer gases vent out into the sky.

Even though it's not visible, the same basic drain setup is functioning behind or beneath your tub and shower (C).

The U-shape of the P-trap holds a small amount of water after each use of the sink, creating a barrier against sewage odors. When everything is functioning correctly, the water remains in the P-trap after you turn off the sink, empty the tub, or flush the toilet. This small amount of water is sufficient to prevent gases from escaping the sewage system and entering your home. Under normal conditions, these gases flow past your bathroom and exit through the vent pipe on your roof.

The Importance of the P-Trap

"The role of the P-Trap is to keep the sewer gases out of the home," says Ray Patrick, a master plumber with Roto-Rooter. "There are misconceptions that the traps are also there to catch objects that might be dropped in the drain, which is not the case. Traps are there to prevent sewer gases from escaping into the home."

Failure to properly vent those stinky gases has the potential to be more than just annoying.

"It could be dangerous because of other gases that can be present in sewer systems. Methane is the largest cause of sewer smell but there is also danger of hydrogen sulfide, carbon dioxide, ammonia, nitrogen oxides and sulfur dioxide," explains Patrick in an email interview, adding that the main culprit of such added toxins are people disposing of gasoline and other chemicals down their drains.

Signs of exposure can include dizziness, headaches, nausea and drowsiness. Clearly, it's important to figure out exactly what's causing the sewage smell and make sure it's corrected quickly and effectively.

7 Fixes for That Sewage Smell

There are a few fixes you can try before calling the plumber.

1. Unclog the Drain

• Effort level: Low, can typically do without seeking help

A clogged drain is kind of gross but fairly easy to resolve. Often, a plunger can take care of the clog, but if that doesn't work a plumber might have to use a drain snake or hydro-jetter to remove it. Sometimes, it's necessary to completely remove the P-trap to solve the issue.

If the suggestions above don't lead you to the source of the sewage smell, you may be dealing with a more complicated issue.

2. Fill the the P-trap

• Effort level: Low, can handle on your own

A dry P-trap is by far the easiest to fix, and more likely to occur in your bathroom if you haven't used the fixtures recently. For example, you may not use the sink in a guest bathroom or the tub in a bathroom with a separate shower.

The issue in situations like these is that the water in the P-trap has simply evaporated due to lack of use, effectively removing the barrier between your bathroom and the gases in the sewer system.

If that's the case, the solution is as simple as running some water to allow the P-trap to fill up again. If plain running water isn't making a dent in those sewer odors, Patrick recommends using pink RV water-safe antifreeze.

3. Check the P-Trap for Leaks

• Effort level: Easy to detect but fixing might require professional help

If there's still a sewage odor after you've run plenty of water or pink antifreeze down all the drains or if you notice sewer smells in a bathroom that gets regular use, check for leaks in or around the P-trap.

If even a small amount of leaks out of the bottom of the "U," sewage gases may be able to sneak in. "If anything leaks, it would be noticeable," Patrick explains.

To fix a leaky P-trap, first, place a bucket underneath it to catch any water and turn off the water supply. Then, carefully loosen the slip nuts on both ends of the P-trap using a wrench and remove the trap. Inspect for cracks or worn-out washers; replace any damaged parts or washers. Seal any cracks or openings. Reassemble the trap tightly, ensuring all connections are secure, then run water to check if the leak has stopped.

4. Address Leaky or Damaged Pipes

• Effort level: Easy to detect but professional help necessary in many cases

Check for visible leaks under sinks and around pipes. Use a flashlight to inspect areas under the sink or behind the toilet, and listen for any dripping sounds. A plumber’s inspection is best for leaks in walls or under flooring.

Minor leaks from accessible areas can be DIY fixes with a plumber’s tape or sealant. For hidden or severe leaks, contact a plumber to prevent further damage.

5. Check if the Toilet Seal Is Intact

• Effort level: Can be a DIY project but involves heavy lifting

To check for issues with the toilet seal, consider performing the following tests:

• Leaks: After flushing the toilet, look for any water pooling or damp spots on the floor around the base. A leaking wax seal often results in water seeping out from beneath the toilet.

• Sniff: A persistent sewage odor near the toilet might suggest a broken wax seal, as sewer gases can escape when the seal is compromised.

• Rock: Gently rock the toilet back and forth. Movement or wobbling could indicate that the wax seal isn't properly sealing the toilet to the floor flange, potentially leading to leaks.

If you want to handle it yourself, follow these steps:

1. Gather the necessary tools: Vaughan HVAC suggests having shims, a putty knife, a washer, caulk, a hacksaw, pliers, an adjustable wrench, and a deep well socket ready.

   
   

2. Remove the toilet: Begin by turning off the water supply, then flush to drain the tank and bowl, and disconnect the water line. Use a sponge and bucket to extract any remaining water from the bowl's trap. Loosen the bolts securing the toilet to the floor, carefully breaking them off if they’re corroded, but be careful not to damage the flange. Once unbolted, lift the toilet straight up, keeping it level to avoid spills.

   
   

3. Scrape off wax: Use a putty knife to remove the wax, ensuring the floor flange is as clean as possible. If you're not replacing the toilet, also remove any wax from its bottom.

   
   

4. Install wax seal: Insert the new Johnny bolts into the floor flange, position the rubber gaskets, and align the toilet over them. Center the wax ring according to the instructions, then lower the toilet, ensuring the bolt holes align with the flange bolts. Tighten the nuts on the bolts, sit on the toilet to secure the seal, and finish by caulking around the base for added stability.

6. Examine the Roof Vent

• Effort level: Achievable, yet potentially out of reach.

To inspect for a blockage in the vent pipe, go to the roof and search for obstructions such as leaves, dirt, or nests. Remove any blockages if you are comfortable with it. If it’s difficult to access or you’re uncertain about clearing it, a plumber can handle this safely.

7. Correct Sewer Line Issues

• Effort level: Consult the experts

If you suspect a sewer line problem, a professional inspection is necessary. Plumbers can utilize cameras to examine the main sewer line and identify any blockages or damage. It's advisable to leave this task to a plumber, as they possess the tools and expertise to handle complex issues such as tree root intrusions or damaged sewer lines.

So, there's water in all the P-traps, no visible leaks, and the pipes are unclogged. What's the next step?

Check Outside the Bathroom

Sometimes, the issue originates elsewhere, even though the odor is present in the bathroom. For instance, a roof vent blocked by a bird's nest, leaves, or snow and ice can stop fresh air from entering the plumbing system, hindering the sewage system from venting properly.

It can be challenging to differentiate between a blocked drain pipe and a blocked vent, which often leads homeowners to concentrate their efforts on a single pipe.

Besides the sewage odor, some indicators that a blocked vent is the real problem include all the drains in the house being slow to empty and water making gurgling noises or bubbling up when draining.

An improperly installed, cut, or cracked vent pipe can also release unpleasant gases into your home. A cracked vent pipe is particularly difficult to locate, as the break is likely hidden within your walls.

Luckily, a plumber can identify a vent pipe leak using a device called a smoke machine, which fills the drain system with harmless visible smoke. When the smoke escapes, the leak source becomes clear.

Hire a Professional

While many of these repairs can be easily handled by the typical homeowner, it's important to assess your own comfort and skill level before starting a project like this. If you're skilled with tools, you might handle tasks like cleaning drains or replacing a toilet's wax ring. However, if you're not confident in doing home repairs or unsure about the source of the odor, it may be wiser to hire a professional.

Sewage Smell FAQ

Why does my bathroom smell like sewage?

There are several reasons your bathroom might smell like sewage, with the most frequent being a lack of water in the P-trap.

How do you get rid of a sewer smell?

To remove a sewer smell due to a dry P-trap, run water in the sink. If that doesn't work, try using antifreeze and check for any leaks.

Is a sewage smell in a bathroom dangerous?

Sewage releases toxic hydrogen sulfide gas, which can damage organs and irritate the respiratory system. However, it's unlikely that the smell from your drains will release a harmful amount, so there's little reason to worry.

Why does my shower water smell like sewer gas?

A typical cause of unpleasant-smelling water is the growth of bacteria in your drains. When food particles and waste accumulate in pipes, bacteria flourish and emit septic gases like sulfur, leading to a rotten egg smell.

How do I fix a clogged drain?

To unclog a drain, try using a plunger to eliminate blockages and any standing water. If this doesn't work, consider using a hydro-jetter or a drain snake.