How to Get Rid of Drain Smell in Bathroom (Step-by-Step Fix)

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If your bathroom drain smells bad, it is usually caused by trapped hair and debris, bacteria buildup, a dry P-trap, or sewer gas coming back up the pipe. The odor develops when organic material collects inside the drain and begins to decompose.

The good news is that most drain smells can be fixed quickly with simple steps.

bathroom sink drain cleaning to remove odor

 

Common Causes of Bathroom Drain Smell

1. Hair and Soap Scum Buildup

Hair, soap residue, and skin oils collect inside the drain pipe. Over time, bacteria break this material down and create a foul odor.

This is the most common cause.

2. Dry P-Trap

The P-trap is the curved pipe under your sink or shower. It holds water to block sewer gases.

If the drain has not been used for a while, the water can evaporate, allowing sewer gas to enter the bathroom.

3. Bacteria Inside the Overflow Drain

Bathroom sinks have a small overflow hole near the top. Moisture and residue inside this hidden channel often cause odor.

Many people forget to clean it.

4. Vent Pipe Blockage

If the plumbing vent on the roof is blocked, sewer gases cannot escape properly. This can force odor back through drains.

5. Mold Growth in Pipes

Constant moisture inside bathroom pipes creates an ideal environment for mold and bacteria growth.

Step-by-Step: How to Remove Drain Smell

Follow these steps in order.

Step 1: Flush the Drain With Boiling Water

Slowly pour boiling water down the drain to loosen soap buildup and kill bacteria.

Do not use boiling water on PVC pipes if your plumbing is old or fragile.

Step 2: Use Baking Soda and Vinegar

  1. Pour ½ cup baking soda into the drain.

  2. Add 1 cup white vinegar.

  3. Let it fizz for 15–20 minutes.

  4. Flush with hot water.

This helps break down organic material.

Step 3: Clean the Overflow Hole

If your sink has an overflow opening:

  • Insert a small brush.

  • Pour diluted vinegar inside.

  • Rinse thoroughly.

Odor often hides here.

Step 4: Check the P-Trap

If the drain hasn’t been used:

  • Run water for 30–60 seconds.

  • This refills the P-trap and blocks sewer gas.

If smell continues, the trap may need cleaning.

Step 5: Remove and Clean the Trap (If Needed)

Place a bucket underneath.

Unscrew the P-trap and remove debris inside.

Rinse thoroughly and reinstall.

How to Prevent Bathroom Drain Odor

  • Use a drain hair catcher.

  • Flush drains weekly with hot water.

  • Avoid pouring grease or heavy residue down drains.

  • Clean overflow holes monthly.

  • Run unused drains occasionally to keep the trap filled.

Frequently Asked Questions

Why does my bathroom smell like sewage but the toilet is clean?

The smell often comes from the sink or shower drain, not the toilet.

Why does the drain smell worse at night?

Temperature changes and reduced water use can make sewer gas odors more noticeable.

Can bleach fix drain smell?

Bleach may temporarily reduce odor but does not remove buildup inside pipes.

When should I call a plumber?

If the smell continues after cleaning and checking the P-trap, there may be a vent or sewer line issue.

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