Why does my floor trap smell even after cleaning?
A Singapore answer for HDB, condo and landed bathrooms — what a licensed plumber checks, and what it costs before any hacking.
Why does my floor trap smell even after cleaning?
A floor trap in a Singapore flat or condo smells after cleaning because the odour is below the cover you washed: either the water seal has dried out, or grease and hair sit packed inside the bend. A PUB-licensed plumber checks the trap water level, the bend and the vent before quoting.
Cleaning the strainer removes what you can see. The trap is the U or bottle-shaped fitting under it, and it works by holding a shallow layer of water that blocks sewer gas. When that layer is gone — dried out in a spare bathroom, or pulled out by pressure changes when another fixture drains — gas comes straight up. When it is still there but the bend is coated with grease and hair, the trap itself becomes the source of the smell.
Symptom to cause: what is actually wrong
| What you notice | Most likely cause | What a licensed plumber checks |
|---|---|---|
| Smell only in a bathroom nobody uses | Water seal has evaporated | Water level in the trap, then run a tap for ten seconds |
| Smell returns days after cleaning the strainer | Hair and grease packed inside the bend | The trap body below the strainer; rod the bend, not just the cover |
| Gurgling when the basin or WC empties | Trap siphoned empty by another fixture | Anti-siphon valve, vent and trap depth |
| Smell plus slow draining | Partly choked branch behind the trap | Access eye, rod or camera, and the fall of the run |
| Smell at the WC base or pipe box, not the trap | Failed collar seal or a cracked joint | Seal test and joint inspection, with no-hack options first |
| Kitchen line serving an F&B unit smells | Grease coating the pipe wall downstream | Grease interceptor level and pump-out schedule |
Updated 27 Oct 2026. Table is diagnostic guidance, not a remote diagnosis — a trap body or joint can only be confirmed on site.
What happens when you engage AOT
Send a photo of the trap and your postcode on WhatsApp. For a straightforward smelly or slow trap we give a from-price before attending; if the trap body, a concealed joint or the branch behind it is suspect, we survey first from $50 and quote the scope before any hacking. Choke or trap clearing starts from $60. Labour only — parts and GST are extra. We water-test before leaving and tell you what to watch for.
Coverage is islandwide Singapore, Monday to Saturday 08:00–17:00. We are not a 24-hour service, so we will tell you honestly when we can attend.
Common questions
Why does my floor trap smell even after I clean the strainer?
Cleaning the strainer or cover only reaches the top of the trap. The smell usually comes from the water seal, the bend directly below it, or grease coating the pipe wall downstream.
Will pouring bleach down the floor trap fix it?
Bleach suppresses the smell for a few days but does not remove the hair and grease holding it. If the smell is back within a week, the trap needs rodding rather than more chemical.
Do I need to hack the floor to fix a smelly floor trap?
Usually not. Most cases are cleared through the trap or its access eye. Hacking is only needed for a cracked trap body or a shifted joint, and that scope and price is quoted before any work starts.
Is a smelly floor trap dangerous?
The smell is sewer gas coming back through a dry, shallow or broken trap. It also lets pests in, which is why a trap that keeps drying out should be corrected rather than masked.
How much does it cost to fix a smelly floor trap in Singapore?
Site survey from $50, and choke or trap clearing from $60 for straightforward cases. Concealed pipe or trap-body replacement is quoted after survey, with the price confirmed before work.
Related: choked drain and trap clearing · why a drain chokes again · leak repair · concealed vs surface leak · full from-rates
Smell coming back after every clean?
Send the trap photo and postcode — we will tell you whether it is a seal, a bend or a joint.