Plumbing Basics · 8 min read · Beginner

How to Clean or Replace a Sink Trap

Understand the trap under a basin or sink, remove it without flooding the cupboard and refit compatible compression joints without overtightening.

Key points & steps

Identify the trap type and pipe size before buying replacement parts. Basin and sink wastes can use different sizes and configurations.
Clear the cupboard and place a wide bucket directly underneath the trap because the water seal and waste pipe can release dirty water when opened.
If the problem is a blockage, try ordinary drain-clearing methods first. If the blockage appears to be in the trap, loosen the removable compression nuts while supporting the trap body.
Lower the trap carefully and empty the water into the bucket. Inspect for debris, damaged washers, split plastic, distorted threads or perished seals.
Clean reusable components and make sure compression washers are present, correctly oriented and seated. Replace damaged parts rather than trying to compensate by overtightening.
Refit the trap squarely so the pipework is not under sideways strain. Hand-tighten plastic compression nuts, then follow the product instructions if any further tightening is specified.
Run water for several minutes and inspect all joints. Fill and release the basin/sink to give the waste a higher-flow test, then check again for drips.
If the waste pipework does not line up, is cracked, leaks inside a wall/floor, or the blockage is deeper in the drainage system, stop and get plumbing help.

Do not use excessive force on plastic compression nuts; distortion can create the leak you were trying to fix.
A trap is designed to retain a water seal that blocks drain odours, so an improvised straight connection is not a substitute.
Take a photo before dismantling unfamiliar pipework so you can reproduce the original arrangement.