Why is there a sewer odor in my bathroom?

If you are dealing with constant unpleasant odors lingering in the bathroom, it is time to take effective action. Sewer odors in the bathroom indicate some type of plumbing problem that should be resolved, as sewer gas is unhealthy. You can perform a basic DIY investigation to pinpoint the source of the problem.

One Unwanted Smell, Several Possible Causes

Even when your bathroom is clean and sanitized, you detect an unpleasant sewer smell. A sulfurous odor in your bathroom could originate from several possible sources.

Keeping Sewer Smells in the Sewer

Your sink, bathtub and toilet are all connected to a sewage system, and it is normal for sewer gases to form within that system. Your plumbing has features to cause these gases to stay in the pipes, keeping sewer smells where they belong – and not in your home. It can be helpful to review the pieces of the system in place in your home works to keep these gases controlled correctly.

Plumbing Traps

Generally referred to as “P-traps,” plumbing traps are the U-shaped pipes that you can see under your sink. Similar systems are out of sight behind or underneath your toilet and your tub or shower.

It’s a common misconception that these curved pipes are in place to catch objects that fall into the drain and keep them from entering the sewer line. Instead, their real purpose is to keep sewer gases from returning up the sewer and into the home. The curve in the pipe enables it to collect some amount of water, and the water acts as a barrier that prevents gas from exiting the pipe.

Methane may have the worst odor of any sewer gas, but the P-trap also helps keep other hazardous (and unpleasant smelling) gases out of your bathroom, including sulfur dioxide, ammonia, hydrogen sulfide, nitrogen oxides and carbon dioxide. Some of these are present as a result of chemicals that may have been poured down a drain.


The P-trap also connects to a pipe that goes up the wall and out through the roof. This is an additional outlet for sewer gases and it also serves to allow fresh air into the bathroom. If the system is working as intended, the water in the P-trap prevents gases from entering the drain for your sink, tub or toilet and, instead, they flow up the vent and out of the home.

Where to Look First: Simple Solutions

If your P-traps or vents aren’t working properly, you will notice a constant, unpleasant (and unhealthy) sewer smell. It is possible that some simple steps can resolve your problem easily.

  • P-Traps: if you haven’t used the bathroom sink or tub in a while, the water in the P-trap could have evaporated. Run some water (a few cups worth). Wait an hour and look into the drain to see if you can still see some water. (You may also notice that the sewer smell is gone.)
  • Vents: Leaves, a bird nest or other debris can block a vent. If your drains are slow and the water bubbles or makes gurgling noises as it is emptying, that can be a sign that your vent is blocked. If you know how to find the vent, you can get on the room and inspect it – but exercise great caution, or call Benjamin Franklin Plumbing in Kansas City.

There’s also a possibility that a vent pipe is cracked or even that it was not properly installed in the first place. This is the kind of problem that our Ben Franklin Plumbing technician can quickly diagnose and repair. We have all of the most advanced diagnostic technology to identify and repair plumbing problems, including a smoke-producing machine that fills the system with non-toxic smoke. If there’s a leak, it reveals the location when the smoke exits the system.

Could it Just be a Clog?

It could be the case that what you’re smelling is material that is trapped in the pipe due to a clog. Try using a plunger to release the clog. If you decide to plunge the toilet as well, remember to use a plunger designed for a toilet. Rather than being flat across the bottom, these have a flap in the center that fits into the drain. If this does not resolve your problem, it doesn’t mean you’re all out of options.

What About the Toilet?

The toilet would seem be the first place to look if your bathroom smells of sewage. However, the toilet bowl, when full, acts as an additional barrier to gases. If you notice that the bowl is not as full as you expect it to be, that could be a sign that the seal at the bottom of the toilet is broken. If your toilet is loose or wobbly, the wax toilet ring in which it sits may be damaged.

Smells can also be caused by water, or urine, seeping under the base of the toilet and providing a breeding ground for bacteria. This can occur when there is no caulk around the base of the toilet and applying caulk around the bottom of the toilet may resolve the issue.

These are simple problems for a technician from Benjamin Franklin Plumbing in Kansas City to fix if you’re reluctant to take them on yourself.

Musty Odors

Does the smell from your drain have a musty or mildewy quality? That could be caused by mold that is growing within the system. Mold spores emit gas that is both odorous and, in some cases, toxic. As a preliminary test, you can run water into a musty-smelling drain for a few minutes. If it is slow to drain, that can be a sign that material has accumulated in the drain.

Here’s a home remedy that you can try to resolve this issue:

  • Put the tip of a funnel into the drain
  • Put a half a cup of baking soda into the drain through the funnel
  • Pour a cup of white vinegar into the funnel and pull it out
  • After 15 minutes, or when the froth from the baking soda settles, run hot water down the drain for one minute
  • After 5 minutes, run cold water down the drain

Do not try this remedy if you have recently used a chemical drain cleaner. If the mold smell does not go away, the drain may require a professional cleaning. It’s also possible that the moldy smell, and the mold problem itself, is originating from another area of the bathroom.

When Should I Call a Plumber?

If you don’t have the time, interest, experience or tools to take on plumbing repairs yourself, call Benjamin Franklin Plumbing in Kansas City to find and repair the source of sewer odors in your bathroom (or other area of the home). The underlying cause can be identified and repaired, and your home environment left smelling sweet and clean once more.

There is no single reason for sewage smells in the bathroom. An experienced plumber from Benjamin Franklin Plumbing will get to the source of the problem – which may be more than a single issue. While it’s not likely, the odor could be a sign of a bigger problem that should be addressed before it worsens, requiring more expensive repairs. There’s a certain piece of mind that comes from knowing your entire plumbing system is in good working order – especially before the cold winter weather hits.

There’s another good reason to seek a professional evaluation. If any part of your bathroom plumbing system was improperly installed, whether a toilet ring or a vent pipe, you cannot correct your problem by clearing a drain or caulking the base of the toilet. If you’re not a plumber yourself, you won’t be in a position to identify the departures from standard plumbing installation practices. You’d be surprised what our team has found over our many years resolving plumbing problems!

The Benjamin Franklin Plumbing Difference

If you need help, Benjamin Franklin Plumbing in Kansas City is known for providing expert – and affordable — service, delivered on time by skilled and highly-trained professionals. If we don’t arrive at the time scheduled for your appointment, we’ll even pay you $5.00 for every minute we are late! We know your time is valuable, and we treat you and your home with respect.

Our Benjamin Franklin Plumbing technicians ensure our customers understand exactly what needs to be done, why, and what it will cost, and they don’t get to work until you have approved the job. When the work is done, they’ll ensure your home is clean and tidy before they leave. If they fail to do so, you won’t have to pay for your service. We value our customers!

In addition to our repair services, Benjamin Franklin Plumbing can help you discover the latest innovations in plumbing technology, from hands-free and web-enabled fixtures to highly efficient options that can help you save on your water bill.