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Fix a drain that smells

We'll refill a dry P-trap, check the vent, and clean bacteria buildup—or tell you when to call a plumber.

Troubleshooting · Home plumbing
15–30 min
What you'll need
  • Baking soda and white vinegar
  • Access to the roof for vent check (optional; call a pro if unsafe)
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Steps

Goal: Confirm which drain smells, refill the P-trap, clean bacteria, check the vent, or call a plumber when needed.

  • Identify the drain—sink, shower, tub, or floor drain. If the smell is strongest at one drain, the issue is likely that drain or its trap.
  • Good: One drain smells worst—local issue. Proceed to Refill P-trap.
  • Bad: Smell throughout the house—main vent or sewer line. See When to get help.

Refill P-trap

Goal: Run water to refill a dry P-trap—the most common cause of drain smells.

  • Run the faucet or shower for 30–60 seconds to refill the P-trap. For a floor drain or unused drain, pour a quart of water down it. Wait a few minutes and check if the smell fades.
  • For drains that sit unused, pour water down them weekly to keep the trap full.
  • Good: Smell fades—trap was dry. See Verification.
  • Bad: Smell persists—proceed to Clean the drain.

Clean the drain

Goal: Reduce bacteria buildup with baking soda and vinegar.

  • Pour half a cup of baking soda into the drain, then half a cup of white vinegar. Cover the drain with a wet cloth and wait 15–20 minutes. Flush with hot water.
  • Good: Smell reduced—bacteria buildup. See Verification.
  • Bad: Smell persists—proceed to Check the vent.

Check the vent

Goal: Verify the vent pipe is not blocked.

  • The vent pipe runs to the roof. From the roof, look into the vent—you should see daylight. If blocked by leaves, birds, or ice, clear it carefully or call a plumber. Do not go on the roof if it is icy or you are not comfortable with heights.
  • Good: Vent clear—smell may be from another cause. Call a plumber if it persists.
  • Bad: Vent blocked—clear if safe, or call a plumber.

When to get help

Call a plumber if:

  • The smell persists after refilling the trap and cleaning.
  • The vent is blocked and you cannot clear it safely.
  • You smell natural gas (rotten egg odor from the utility)—evacuate and call the gas company.

Verification

  • The drain no longer gives off sewer gas or foul odors.
  • Running water for 60 seconds does not bring back the smell.
  • Pour water down unused drains weekly to keep the trap full.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm which drain Identify the drain that smells worst.
  2. Refill P-trap Run water or pour water down the drain to refill the trap.
  3. Clean the drain Use baking soda and vinegar to reduce bacteria.
  4. Check the vent Look at the vent pipe on the roof for blockages.
  5. Call a plumber Smell persists, vent blocked, or gas smell—call a pro.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Which drain smells
  • Whether the drain is used regularly
  • Steps already tried (run water, baking soda/vinegar, vent check)
  • Whether the smell improved

Does running water reduce the smell?

A dry P-trap is the most common cause. Run water for 30–60 seconds to refill it.

Run the faucet or pour water down the drain for 30–60 seconds. Wait a few minutes. Good: smell fades—trap was dry. Bad: smell persists—proceed to clean and check vent.

Yes No

You can change your answer later.

Did baking soda and vinegar reduce the smell?

Baking soda and vinegar reduce bacteria in the drain.

Pour half a cup baking soda, then half a cup vinegar. Cover, wait 15–20 minutes, flush with hot water. Good: smell reduced—bacteria buildup. Bad: smell persists—check vent or call a plumber.

Yes No

You can change your answer later.

Is the vent pipe blocked?

The vent on the roof lets air into the drain system. Blocked vents cause odors.

From the roof, look into the vent pipe. You should see daylight. Good: vent clear—smell may be from another cause; call a plumber. Bad: vent blocked—clear it if safe, or call a plumber. Do not go on the roof if icy or you are not comfortable.
Question

Is the vent pipe blocked?

Continue

You can change your answer later.

Smell resolved

The drain no longer smells. Pour water down unused drains weekly to keep the trap full. Install a drain screen to reduce debris.

Done

Call a plumber

Call a plumber if the smell persists after refilling the trap and cleaning, the vent is blocked and you cannot clear it, or you smell natural gas—evacuate and call the gas company. Sewer smell that does not improve suggests a vent or pipe issue.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does a drain smell?
A dry P-trap is the most common cause—water evaporates and sewer gas enters. A blocked vent can cause slow drainage and odors. Bacteria buildup in the drain can also produce smells.
Can I fix a smelly drain myself?
Yes. Run water to refill a dry P-trap. Check the vent on the roof for blockages. Clean the drain with baking soda and vinegar. Call a plumber if the smell persists or the vent is blocked.
When should I call a plumber for a drain smell?
Call a plumber if running water does not stop the smell, the vent is blocked and you cannot clear it, or you smell gas (not sewer gas)—that could be a gas leak. Sewer smell that persists after refilling the trap suggests a vent or pipe issue.

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