Why Does My Shower Drain Smell Like Sewage?

A foul sewage smell coming from your shower drain is never a pleasant experience. However, there are several common causes behind this unpleasant odor. Identifying the source of the smell is the first step towards eliminating it for good.

Common Causes of Sewage Smell in Shower Drains

Buildup of Organic Matter

Over time, hair, skin cells, soap scum, and other organic matter can accumulate in shower drains. As this buildup decomposes, it can emit a foul, sewage-like odor. Regularly removing this organic matter by snaking or cleaning your drain can help combat smells.

Clogged Vents

Most home plumbing systems have vent pipes that allow air to enter and exit the system. If these vents become clogged with debris, it can cause airlock in the pipes and allow sewer gas smells to backflow up the drain. Having a professional inspect and clear debris from vent pipes may fix the issue.

Cracked Sewer Line

Damage or cracks in the main sewer line running from your home can allow sewer gases to infiltrate into the drainage system. Sewer line video inspection can identify leaks or cracks. Repairing or replacing damaged sections of sewer pipe will be needed to stop the smell.

Dried Out P-Trap

P-traps are the U-shaped pipes under sinks and showers that hold water to block sewer gas from entering. If this water evaporates over time, gases can sometimes backflow into the drain. Simply pouring water down infrequently used drains refills the trap and blocks smells.

Improperly Installed Drain

If shower drains were installed improperly or have come loose over time, it can disrupt the trap seal and allow odors to escape. A plumber may need to tighten fittings, re-slope pipes, or completely replace faulty drain connections.

Sewage Backup

A blockage deeper in the main sewer line can cause widespread drainage issues and back sewage up into shower drains. This will cause very foul odors until the main blockage is identified and cleared. A drain service professional will be needed for significant sewer clogs.

Diagnosing the Exact Source of the Odor

Pinpointing the origin of a sewage smell in a shower drain often takes some detective work. Start by seeing if any other drains exhibit the odor. Try pouring water into floor drains, sink drains, etc. to isolate the issue. Using a small mirror, inspect the shower drain itself for any buildup, damage, or cracks.

Running water for 15-20 minutes can also help determine if filling the P-trap fixes the smell temporarily. If the odor seems to come from the overflow drain specifically, cleaning or replacing its mechanical stopper may help. Tracing pipes back to vent locations also helps identify blockages. Odors noticed only during shower use point to buildup as a likely cause.

How to Eliminate Sewage Odors from Your Shower Drain

Once the source of the odor is identified, steps can be taken to eliminate it.

Clean the Drain

For simple buildup, mix baking soda and vinegar to break down organic matter, then flush with boiling water. Use a zip tool to remove hair clogs. Strong enzymatic drain cleaners can also help break down oils and soaps.

Clear Clogged Vents

Call a plumber to inspect vents and clear any obstructions. They may also check vent height and positioning to ensure proper functioning. Installing vent filters can prevent future debris clogs as well.

Repair Sewer Line Leaks

Significant cracks or leaks in sewer lines will require professional repair or full replacement of damaged sections. Stopgap measures like sealing small cracks may temporarily contain smells.

Re-fill P-Traps

Pour around 1-2 cups of water directly into shower and sink drains to reestablish the water barrier in P-traps and prevent airlock.

Reinstall Drain Properly

A professional plumber can ensure drains have proper slope and are tightly sealed to fixtures using threaded fittings, rubber gaskets, metal clamps or silicone.

Clear Main Sewer Clogs

For suspected main line clogs, call a sewer cleaning service. They can clear obstructions with augers, high pressure water jets, or drain cables inserted from the main cleanout.

Preventing Future Shower Drain Sewage Smells

To help avoid foul odors coming from shower drains in the future:

  • Use drain strainers to catch hair and debris before it enters pipes
  • Pour a kettle of boiling water weekly down seldom used drains
  • Use a biodegradable foaming drain cleaner monthly to break up buildup
  • Have vents cleaned annually to remove any accumulated debris
  • Install an inline vent filter to prevent vent clogs
  • Keep P-traps full by running water briefly down drains after long periods of non-use
  • Avoid pouring fats, oils and harsh chemicals down drains
  • Call a professional immediately at any signs of damage or backflow

Addressing a sewage smell promptly, identifying the source, and taking appropriate action can help restore clean, odor-free shower drainage and prevent unpleasant odors from returning. With proper maintenance, clogs and leaks can be avoided, letting you enjoy your bathroom without embarrassing odors.

Frequently Asked Questions About Sewage Smells in Shower Drains

What causes a sewage smell in my shower drain?

Common causes include buildup of hair and debris in the drain, clogged vents preventing air circulation, cracked sewer lines allowing gas infiltration, dried up P-traps, and main sewer line backups sending sewage upwards.

Why does my shower drain smell when the water is running?

This is likely caused by organic matter buildup in the drain itself, which gets disturbed and emits odor when the shower is used. A thorough drain cleaning should help eliminate smells.

How do I get rid of the smell coming from my shower drain?

Cleaning the drain, clearing vent obstructions, refilling P-traps, repairing cracks or damage in sewer lines, and unclogging main blockages are common ways to eliminate odors from shower drains.

Should I be concerned about sewer gas smell in my bathroom?

Yes, exposure to hydrogen sulfide and other sewer gases can be hazardous. The smell is also a sign of an underlying issue that needs to be addressed, such as cracked pipes, failing vents, or drainage backups.

Does sewer gas smell hurt you?

Hydrogen sulfide gas from sewers can cause eye and respiratory irritation, nausea, headaches, and fatigue at high concentrations. Long-term exposure has been linked to neurological effects. Consult a doctor if exposure results in symptoms.

When should I call a plumber for shower drain smell?

Contact a plumber if DIY drain cleaning and odor elimination efforts fail, if the smell also affects other drains, or if you suspect the issue is caused by damaged plumbing, clogged vents, or main sewer line backups requiring professional repair.


A foul sewage odor coming from your shower drain can be unpleasant and embarrassing, but is usually fixable. In most cases, the smell is caused by buildup in the drain itself, clogged vents, dried out P-traps, or minor drainage system issues. Taking time to identify the source of the smell and implement targeted solutions will help restore clean, odor-free shower use. Don’t hesitate to call in a professional plumber if significant plumbing repairs are needed. With some diligent detective work and appropriate corrective action, you can eliminate unwelcome sewer smells from the shower and prevent their return.