Published 2 June 2026 · 4 minute read · by the Mealdesk crew
Open the cabinet under your sink. That U-shaped bend in the pipe is not a plumber's whim — it permanently holds a cupful of water, and that little pool is the only thing standing between your kitchen and the sewer's atmosphere. When a sink starts to smell, the trap is almost always where the story is.
Smell number one: rotten egg, constant
A steady sewer smell usually means the water seal is gone. Three common ways it disappears:
- Evaporation. A sink unused for weeks — a rental between tenants, grandma's house — simply dries out. Cure: run the tap for ten seconds. Genuinely, that's the fix.
- Siphoning. If the drain line runs too long without venting, a big drain-down (emptying a full basin) can suck the trap dry behind it. You'll often hear a glug-glug as the seal leaves. This one needs re-piping or an anti-siphon valve — a plumber job.
- The invisible bypass. In many Malaysian kitchens the sink hose just pokes into a floor gully. If it sits above the gully's water line, smells walk straight in around it. Cure: extend the hose below the water level or seal the gully collar.
Smell number two: sour funk, worse when water runs
If the smell rises with use, the trap seal is fine — the trap itself is dirty. Years of grease, soap and food starch line the pipe like plaque. Unscrew the trap base (pail underneath), scrub it out, refit, run water. Five minutes, zero cost. If the smell returns within days, the buildup extends beyond reach down the line, and that's when machine clearing earns its fee.
Smell number three: damp cabinet, musty
Not the trap's contents — the trap's joints. A weep so slow it evaporates before pooling will still soak chipboard cabinets into that unmistakable mustiness. Dry everything, lay a sheet of newspaper, and check it after 24 hours. Spots mean a failing washer or cracked compression ring: cheap parts, but worth fixing this week, not this year — chipboard doesn't forgive.
When to stop DIY-ing
Cleaning a trap is honest homeowner territory. But recurring smells after cleaning, gurgling from other drains when the sink empties, or any smell paired with slow drainage across multiple fixtures points to the main line — and pushing harder from the sink end just compacts the problem. That's the point where a camera down the pipe answers in minutes what guesswork answers in months.