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Fix a trap that is dry

We'll confirm the trap is dry, refill it, and find the cause if it keeps draining—or tell you when to call a plumber.

Troubleshooting · Home maintenance
5–30 min
What you'll need
  • Water (to refill trap)
  • Wrench (if tightening or replacing trap)
  • Replacement trap (if leaking)
Step 1 of 6

Quick triage — pick your path

Quick triage — pick your path

Choose the option that matches what you see. You can jump straight to that section.

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Steps

Goal: Confirm the trap is dry, refill it, and find the cause if it keeps draining.

  • Check for sewer smell or pour water down the drain—if it runs through, the trap is dry.
  • Good: Trap is dry. Proceed to Refill trap.
  • Bad: Trap has water—no action needed.

Refill trap

Goal: Restore the water seal by pouring water down the drain.

  • Pour a quart of water down the drain. The trap should fill and hold.
  • Good: Trap holds water and the smell stops. Run water periodically in unused drains.
  • Bad: Water drains away—check for leaks or siphonage.

Check for leaks

Goal: Find and fix leaks that prevent the trap from holding water.

  • Inspect the trap and slip nuts. Tighten or replace if leaking. If the trap drains when the drain is used, the vent may be clogged (siphonage)—call a plumber.
  • Good: Leak fixed or vent cleared. Trap holds water.
  • Bad: Trap keeps going dry—call a plumber.

When to get help

Call a plumber if:

  • The trap keeps going dry after refilling.
  • The trap leaks and you cannot fix it.
  • You smell sewer gas and refilling does not help.
  • You suspect a vent or drain blockage.

Verification

  • The trap has water and holds it.
  • No sewer smell.
  • No leaks at the trap or connections.
  • Unused drains are refilled periodically.

Escalation ladder

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

  1. Refill trap Pour water down the drain to restore the seal.
  2. Check for leaks Inspect the trap and connections for leaks.
  3. Suspect vent If trap drains after use, vent may be clogged.
  4. Call a pro Trap keeps going dry, leaks, or vent issue—call a plumber.

What to capture if you need help

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

  • Whether the trap holds water after refilling
  • Any visible leaks
  • How often the drain is used
  • Steps already tried

Is the trap dry? (Sewer smell or empty trap)

A dry trap lets sewer gas in. You may smell it. The trap is the U- or P-shaped pipe under the drain.

Check for sewer smell or pour water and listen—if it runs through, the trap was empty. Good: trap is dry—refill. Bad: trap has water—different issue.

Yes No

You can change your answer later.

No action needed

The trap has water. The seal is intact.

Done

Pour water to refill

A quart of water restores the seal.

Pour a quart of water down the drain. The trap should fill and hold. Good: trap holds water, smell stops. Bad: water drains away—check for leak or siphonage.

Yes No

You can change your answer later.

Trap refilled

The trap has water and the seal is restored. Run water periodically in unused drains to prevent evaporation.

Done

Is the trap leaking or does it drain after use?

A leak prevents the trap from holding water. Siphonage pulls water out when the drain is used.

Check the trap for leaks. Tighten slip nuts or replace the trap if leaking. If the trap drains when the drain is used, siphonage (vent problem) may be the cause—call a plumber.
Question

Leak or siphonage?

Continue

You can change your answer later.

Call a plumber

Call a plumber if: the trap keeps going dry, the trap leaks, or you suspect a vent (siphonage) issue.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a trap go dry?
Evaporation (drain unused for weeks), a leak in the trap, or siphonage (a blocked or missing vent pulls water out of the trap). Refill first; if it drains again, check for leaks or vent problems.
Can I fix a dry trap myself?
Yes. Pour a quart of water down the drain to refill the trap. If it stays full, you are done. If it drains again, check for leaks or call a plumber for vent issues.
When should I call a plumber for a dry trap?
Call a plumber if: the trap keeps going dry after refilling, the trap leaks, you smell sewer gas and refilling does not help, or you suspect a vent or drain problem.

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