A drain smell can range from a faint mustiness near the plughole to a strong sewage odour in the garden. The source is usually one of the following, and some are easy to fix yourself.
Inside the house
A dried-out trap
Every sink, bath, shower and toilet has a trap: a bend that holds water to stop drain gases coming back into the room. If a fitting is not used for a while, as often happens in spare bathrooms and holiday lets, the water evaporates and the smell comes through.
Fix: run water through the fitting for a minute. If the smell stops, that was the cause.
Build-up in the trap or waste pipe
Hair, soap, grease and food residue decompose inside the pipe and smell. Cleaning the trap usually helps.
A siphoned trap
On some systems, water draining from one fitting can suck the water out of another fitting’s trap. If you hear gurgling from a basin when the bath empties, and then notice a smell, this may be happening.
A failed seal
Seals around toilet pans and soil pipe connections can deteriorate, letting smells escape. You may notice the smell is strongest around the base of the toilet.
Outside the house
Grease in the kitchen gully
A gully coated with grease and food smells, especially in warm weather. Cleaning it out usually solves the problem. See drain cleaning.
A blocked or slow drain
When waste cannot flow away, it sits in the drain and decomposes. A smell combined with standing water in an inspection chamber points to a blockage. See blocked drains.
A damaged pipe
Cracks and displaced joints let sewage leak into the surrounding ground. You may notice a persistent smell with no visible blockage, damp patches or unusually lush grass along the line of the drain, or even rats. A CCTV drain survey can find the damage.
A loose or broken inspection chamber cover
If a cover does not seal properly, smells escape. Check covers are seated correctly and not cracked.
When to call a professional
- The smell persists after running water and cleaning traps.
- You can smell sewage outside with no obvious cause.
- There is standing water or waste in an inspection chamber.
- You have seen rats around the property.
These usually point to a blockage or damage that needs investigating. If the pipe is damaged, drain repairs will stop the smell coming back.
For Southampton properties, see our CCTV drain surveys in Southampton page or contact us.