Bad smell from toilet or floor drain
Not sure if this matches your problem?
Use our interactive tool — answer a few questions and get a personalised diagnosis.
Most likely cause & what to check
A sewage smell from around the toilet most commonly comes from one of three sources: a dry trap, a failed pan-to-soil-pipe seal, or a cracked soil pipe.
Check the toilet trap — if the toilet is rarely used, the water seal in the trap can evaporate, allowing sewer gas to enter the room. Flush the toilet and pour a litre of water into the pan to re-establish the seal.
Check the silicone seal at the base of the toilet where it meets the floor — if this has failed, sewer gas and waste can seep out. Remove the old silicone and reseal with sanitary-grade silicone.
If the smell persists despite these checks, the soil pipe connection at the back of the toilet may have a failed rubber doughnut seal. This requires pulling the toilet forward slightly to access and replace the seal.
A persistent smell with no visible cause may indicate a cracked soil pipe behind the wall — a drainage engineer with a CCTV camera can diagnose this.
Prefer to have it done for you?
Find me an engineer →🛠 Tools & materials you may need
Get a vetted local engineer to handle it — no hassle, Gas Safe registered.
Was this guide helpful?