Shower Drain Smells Like Sewage: Causes and Fixes

A homeowner’s bathroom isn’t just functional; it often serves as a respite, giving people a place to relax and wash off the day or reinvigorate themselves in the morning. When you walk into the bathroom only to be hit with a foul odor emanating from your shower, it’s a shock. As a result, the only thing on your mind is usually figuring out why your shower drain smells like sewage and how to fix the problem.

A shower drain may smell like sewage for several reasons. Broken plumbing pipes, clogged drains, and biofilm buildup could be responsible. Sewage backups, full septic tanks, or blocked plumbing vents are other potential causes, though they aren’t the only ones.

Since a shower drain that smells like sewage may occur for several reasons, you need to determine the source of the odor to find a suitable solution. Here’s what you need to know.

Shower Drain Smells Like Sewage

Why Worry About a Shower Drain That Smells Like Sewage

A shower drain that smells like sewage is a concern. The most obvious issue is the unpleasant odor, which makes the space unpleasant.

Additionally, when a shower drain smells like sewage, it typically signals a plumbing issue. Pipe leaks, blocked vents, clogged drains, and many other plumbing system problems can cause sewer gas and waste odors to invade your bathroom.

Sewer gas exposure also comes with health risks. While low levels for short periods aren’t typically harmful, long-term exposure and higher levels can lead to sewer gas poisoning. Plus, components in the gas are flammable, making the sewage smell a potential fire hazard.

Why My Shower Drain Smells Like Sewage

Pipe Leaks

Pipe leaks can cause two issues that may lead to foul odors from drains. First, it may allow sewer gas inside. Second, it could let wastewater exit your plumbing system, causing it to puddle under your foundation, walls, or other parts of your home’s structure.

Drain Clogs

Drain clogs prevent wastewater from moving through your plumbing. Additionally, even if it doesn’t result in a full blockage, the debris can trap waste. Along with the odor created by decomposing material, it could allow sewer gas back into your home.


Biofilm is a slimy buildup that often resembles mold. However, bacterial colonies and waste can create a sticky substance that may block drains or collect drain-blocking debris.

Biofilm can create an odor. Any decaying matter caught in it may also smell. Biofilm is potentially a health hazard, increasing the odds of certain infections.

Damaged Toilet

Loose or damaged toilets may cause sewer gas to leak into your home or waste to sit in the pipes. Additionally, if there’s a gap between the toilet and the underlying pipes, wastewater may end up in or under your foundation or in your walls, which can cause odors to come through nearby drains.

Dry P-Trap

The P-trap in your shower is part of the drainage system that creates a water barrier to prevent sewer gas from home through the drain. If the shower goes unused for a significant period, that water barrier may effectively evaporate. As a result, the dry P-trap lets sewer gas inside.

Grimy P-Trap

Even if the water barrier is intact, your P-trap could still be responsible for the foul odor. Grime can settle in the U-shaped bend in this portion of your drain system, resulting in bacteria or decay that produces a sewage-like smell. An unused shower may end up with a layer of scum over the top of the water barrier, which could create a distinct odor.

Blocked Plumbing Vents

Plumbing vents are systems that extend up onto a home’s roof. The pipes direct sewer gas out of your house, avoiding potential health and safety issues relating to sewer gas building up in structures. Additionally, the vent ensures that air can enter the wastewater portion of your plumbing system, which is critical for flow.

When plumbing vents are blocked, sewer gases can’t escape correctly, and wastewater doesn’t flow properly. As a result, you can end up with a foul odor emanating from your roof or drains.

Sewage Backup

Sewage backups can occur for several reasons. While clogs or blockages in your plumbing are potential causes, broader systemic issues may also be responsible.

Main blockages in city sewer systems aren’t common, but they occur. When those happen, it may prevent wastewater from exiting your home correctly or cause wastewater from other nearby properties to push into your pipes, leading to a sewage backup.

In most cases, main blockages that lead to sewage backups cause foul odors to emanate from more than one drain in your home. However, if the issue is new and your shower drain is closest to the main, the smell may start there before reaching other drains.

Septic Tank Is Full

A full septic tank has an effect similar to the main blockage. Essentially, there’s not enough room for more wastewater in the tank, so the wastewater backs up into the pipes.

How to Fix a Shower Drain That Smells Like Sewage

How to Fix a Shower Drain That Smells Like Sewage

Unclog Drain Lines

1. Start with a Hair Snake

In some cases, clogs near the drain cover can produce odor, since hair is a common cause of those clogs, get a disposable hair snake to remove the blockage.

Take the drain cover off, insert the hair snake into the blockage, and twist it. Pull the hair snake out, remove the debris, and repeat the process until the clog is gone.

2. Use Vinegar and Baking Soda

The bubbling reaction created when you combine vinegar and baking soda may break up a clog if it’s near the entry of the drain. Pour ½ cup of baking soda into the drain, follow that with ½ cup of distilled white vinegar, and place a drain cover over the opening to contain the reaction. Then, flush with hot water to see if the blockage is gone.

3. Try a Plumbing Snake

Use a plumbing snake for stubborn clogs or blockages deeper in the drain. Remove the drain cover, choose a coiled or toothed head, and insert the plumbing snake until you reach the clog. Turn the handle to grab the blockage, then pull out the snake to see if that handles the problem.

4. Move on to an Auger

Augers are often larger than plumbing snakes, so they may work better on stubborn clogs. Go with a cutting head, feed the auger into the drain, and either use the manual crank or turn on the power. Remove the auger, then check for water flow.

5. Contact a Professional

You may need a professional if the options above don’t handle the blockage. They’ll have tools and expertise beyond what most homeowners have, and they can check to ensure there isn’t another issue causing your problem.

Clean P-Trap

1. Run the Water

If you have a foul odor from a shower that wasn’t used recently, simply running the water for a while may fix the issue. That can refill dry P-traps and wash away the film that can occur on stagnate water.

However, even if running the water solves the primary problem, moving on to cleaning is still wise. It ensures you eliminate any remaining grime or buildup, giving you a fresher start.

2. Pour Baking Soda and Vinegar into the Drain

After running the water to ensure the P-trap isn’t dry, pour ½ cup of baking soda into the drain. Next, add ½ cup of white vinegar into the drain.

As soon as you pour the vinegar, cover the drain with a rubber drain stopper or seal it quickly. This contains the bubbling action to ensure it remains in the P-trap area.

Covering the drain also prevents anything caught in the P-trap from overflowing into your shower, essentially containing the grime in the drain. Plus, it can break up minor clogs, which is an extra benefit.

3. Rinse with Hot Water

After the bubbling stops, you can rinse the drain. Use hot water to help flush away any buildup or grime. The hot water can come from the shower, so you don’t necessarily have to heat a water container during this step.

4. Wait a Day or Two

After rinsing, wait a day or two to see if the odor is gone. If it is, that likely solved the problem. If not, you may have another issue or need assistance from a professional plumber.

Remove Biofilm Buildup

1. Remove and Clean the Drain Cover

Removing biofilm is a somewhat manual process. You’ll need a scrub brush and an antimicrobial cleaner that’s safe for your shower material.

Remove the drain cover, and use the brush to break up any attached biofilm. Next, take the antimicrobial cleaner, apply it to the cover, and scrub again. Repeat that process until the drain cover is clean, then set the cover aside.

2. Get a Paint Roller Cover

The fuzzy cover for paint rollers is often suitable for cleaning shower drains. Find one about the width of your shower drain, but don’t attach it to a roller.

3. Soak the Paint Roller Cover in Cleaner

Once you have an appropriately sized paint roller cover, soak it in antimicrobial cleaner. Make sure you’re wearing gloves, as it’s best to keep cleaners off your skin in most cases.

4. Push the Paint Roller Cover into the Drain

After saturating the paint roller cover, stick it down your drain vertically. Ensure several inches remain outside the top of your drain, giving you enough to grab.

Once the paint roller cover is in the drain, twist it back and forth to scrub the biofilm off it. Twist it several times, remove the paint roller cover from the drain, examine the amount of biofilm it removed, and then rinse it with clean water.

5. Repeat Steps 3 and 4

You’ll likely need to scrub the drain with the paint roller cover several times. Repeat steps three and four until you no longer see biofilm when you remove the paint roller cover from the drain.

6. Reinstall the Drain Cover

After removing the biofilm, reinstall the drain cover. Often, rinsing the cleaner isn’t necessary, though you can flush the area if dirt, grime, or debris ends up on your shower.

Fix Leaking Pipes

1. Assess Your Capabilities

Fixing leaking plumbing pipes isn’t simple, and it generally requires expertise. Be honest about your capabilities. If you lack plumbing knowledge, call a professional instead of proceeding with a DIY repair.

2. Locate the Leak

Before taking any other action, you need to locate the leak. If you’re dealing with sewage odors, a drain line is likely involved. Depending on how your home is structured, these may be under your shower pan, in your crawl space, or under your foundation.

Leaks are more likely at joints and connection points, so examine them for drips, discoloration, and loose connections. You can also see if there’s any noticeable puddling to indicate which line is involved. However, puddles can form away from the issue depending on how the wastewater flows, so keep that in mind.

Discoloration, dampness, or odors coming from walls may also show the location of leaks. Again, this isn’t foolproof, particularly if you have second-story bathrooms, as wastewater flowing downward through the walls may not align the stains and dampness with the source of the problem.

Contact a professional if you can’t see the leak or have doubts about its origin. They have additional tools – like moisture detectors and plumbing cameras – which let them identify issues in pipes that aren’t visible.

3. Shut Off the Water

Once you spot a leak, your next step is to shut off your water. Even if you’re dealing with a drain line, you want to prevent more water from entering the system as you work.

4. Put On Appropriate Safety Gear

Repairing a drain pipe means exposing yourself to wastewater. Make sure you put on appropriate personal protective equipment (PPE), including gloves, work boots, shoe covers, eye protection, a respirator, and disposable waterproof coveralls with a hood.

5. Position a Bucket Below the Leaking Pipe

A large bucket under the leak allows you to catch wastewater drips. It ensures the wastewater doesn’t end up anywhere you don’t want it and makes it easier to dispose of later.

6. Move Forward with the Repair

After you have your PPE on and bucket in place, you can move forward with the repair. What that entails varies depending on the nature of the leak.

For cracked pipes or loose joints, epoxy putty gives you a temporary solution until you can replace the damaged section. Follow the manufacturer’s directions regarding the application.

Pipe clamps that are the same length as the pipe and designed to fit that specific pipe width also work for small leaks not originating from joints. For larger cracks, you may want to cut the cracked section of the pipe and apply a slip coupling.

For leaking pipe joints, you have several options. Along with epoxy putty, waterproof silicone repair tape around the joint could be enough for a shorter-term fix. Just make sure to stretch it during application for the best result.

Repairing sleeves are another option. These wrap around the joint and apply pressure to prevent leaks. However, they stretch over time, so they aren’t a permanent solution either.

Otherwise, you may need to detach the pipes and improve the connection. For threaded pipes, starting with Teflon tape on the threaded adapter and adding a layer of pipe joint compound before screwing it back in place may work. Pipe joint compound and plumbing glue may handle unthreaded connections.

Remember that detaching and reattaching plumbing pipes isn’t necessarily a job for amateurs. As a result, it may be better to use a temporary repair and contact a professional for a long-term solution.

Unblock Plumbing Vents

1. Clear Clogs

Sometimes, clogs in your drains or plumbing system can block the vents. As a result, it’s best to start by ensuring your pipes are clear. Use the process above to clear clogs from drains, and check the main clean-out for a blockage.

2. Prepare to Get on Your Roof

If regular clogs aren’t responsible, you’ll need to get onto your roof. Make sure you have a suitable secure ladder and that your roof has a manageable pitch. Choose rubber-soled shoes with good traction, and attach and put on a safety belt for extra security.

In most cases, it’s best to have a helper available to manage tools and stabilize the ladder as you climb. Additionally, choose a day with pleasant weather, as rain, ice, and snow make for slippery conditions.

3. Bring Up and Auger

Usually, an auger is the best choice for clearing a stuck plumbing vent. Choose a manual auger with a suitably long cable, as those give you more control. Plus, they’re typically lighter than their powered counterparts

4. Feed the Auger into the Vent

Once you have the auger on the roof, feed the cable and attached head into the vent. Continue until you reach debris or a blockage.

5. Rotate the Auger and Remove Debris

Once you hit a blockage or debris, rotate the auger clockwise to capture it. Pull the auger back out, remove any stuck debris, and place the waste in a garbage bag.

6. Repeat Steps 4 and 5

After you remove the first chunk of debris or the blockage, repeat steps four and five. Continue repeating those steps until all debris is removed and blockages are clear.

7. Flush the Vent

Once the blockages are addressed, take a garden hose and insert the end into the vent. Turn on the water to rinse the vent and determine if you missed any blockages.

The water should flow freely, so you may need to change tools if it doesn’t. If it does, you’re finished. Wait a few days to ensure the sewer odor clears and, if not, check for other potential causes or contact a professional for assistance.

8. Use a Power Auger

If you flush the vent and the water backs up, bring up a lightweight power auger and use a cutting head. Feed it into the vent until you reach the blockage, then turn the auger on. Stop the auger and pull it out to try and bring up the debris.

You can repeat the process as much as needed to completely address the issue. If any backed-up water in the vent suddenly clears, you may have handled the blockage. Test again with the hose to see if the water flows freely.

If it won’t clear or the water isn’t flowing freely, you may have another issue or require professional assistance.

How to Prevent Shower Drain Odors

In many cases, regular cleanings and consistent usage are the best way to prevent shower drain odors. You can use the P-trap biofilm removal and cleaning processes above to eliminate many types of odor-causing buildup. Turning on the shower regularly can also prevent a dry P-trap.

Preventing clogs is also essential. Avoid rinsing hair down the drain, as that’s a common culprit for shower drain clogs. Additionally, don’t allow children to use small toys in the shower if they can fit in the drain.

For plumbing vent blockage prevention, use a specially designed metal filter cap or cage. That prevents larger debris from getting into the vent, reducing the odds of buildup.

When to Call a Professional

Generally, it’s best to call a professional if you’re uncomfortable handling the repair yourself, don’t have the proper tools, aren’t familiar with plumbing, or can’t find the leak’s origin. Plumbing systems are complex, and small mistakes can have serious consequences.

Beyond clearing minor clogs, addressing P-trap issues, and cleaning drains, hiring a professional is the ideal choice for most homeowners. They can identify the root cause, manage repairs that last, and often have service guarantees, giving you some long-term protection.

Is Sewage Smell in Bathroom Dangerous?

A sewage smell in a bathroom is potentially dangerous. Sewer gas contains various compounds, including ammonia, carbon dioxide, hydrogen sulfide, and methane. At high levels, these gases are potentially toxic.

After exposure to high amounts of sewer gas, a person may experience a variety of systems. Eye, nose, or throat irritation may occur, as well as dizziness, headaches, nausea, fatigue, vomiting, and memory impairments. Organ damage is also possible, as well as even death.

Some of the components of sewer gas are also highly flammable; as a result, the odor-causing gases are a fire hazard.

The Best Way to Fix a Shower Drain That Smells Like Sewage

The best way to fix a shower drain that smells like sewage varies depending on the cause. For clogs or blocked vents, snakes and augers are good choices. Vinegar and baking soda can assist with cleaning and clogs, so it’s worth exploring. However, for extensive issues or unseen and complex leaks, contact a professional.

Did you learn everything you wanted to learn about dealing with a shower drain that smells like sewage? If so, please share the article if you know someone dealing with shower drain odors.

Written By: Yevgen

YevgenI'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.

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