Waste Traps and Seals: Stopping Smells and Slow Drains
The trap under every sink, bath and basin holds a small amount of water that blocks drain smells from coming back up into the room.
The trap under every sink, bath and basin holds a small amount of water that blocks drain smells from coming back up into the room. When traps dry out, crack, or their seals fail, the first sign is usually a smell rather than an obvious leak.
What it does
A U- or P-shaped bend in the waste pipe permanently retains a water seal, physically blocking sewer gas from travelling back up through the pipe into the room.
How it fails
Plastic traps crack with age or from being over-tightened, rubber seals perish, or the water seal simply evaporates from a drain that's rarely used.
Repair or replace
A perished seal or washer is a cheap, quick swap; a cracked trap body is replaced as a whole unit since the plastic itself can't be reliably repaired.
Sort out a smelly or leaking drain
Tell us which sink, bath or drain is affected and whether it's a smell, a leak, or both, and we'll check the trap and seals.
Questions we get asked
Can I replace a trap myself?
Many people manage this themselves with basic tools, since it's usually just accessible pipework under a sink or basin.
Is waste pipework covered by Gas Safe registration?
No, this is plumbing work, not gas work.
Why does an unused drain smell?
The water seal in the trap evaporates over time if the drain isn't used, which lets sewer smell through until the trap is refilled with water.