Why does my drain smell bad?

Locate the source

First identify whether the smell comes from one plughole, a bathroom, an outside gully or several fixtures. Notice whether it appears after running water, during warm weather or when another appliance drains. A local odour may be from residue in a trap, while a persistent sewage smell can point to a drainage or ventilation fault.

Keep the room ventilated and avoid leaning over drains. Never mix bleach with acidic cleaners or other products. Chemical reactions can release harmful gases. If the smell is strongly chemical, leave the area and seek appropriate help rather than adding another cleaner.

Safe household checks

1. 1Remove hair and visible debris from the plug strainer using gloves, then clean the removable parts with ordinary washing-up liquid.
2. 2Run water into a sink, bath or shower that has not been used for a while. A trap holds water to help block drain gases; it can dry out in an infrequently used fixture.
3. 3Check beneath an accessible sink for dampness, loose waste connections or a trap that has shifted. Do not dismantle brittle or corroded fittings.
4. 4Observe whether the smell returns, whether water drains slowly, and whether other fixtures gurgle or back up.

When a plumber should investigate

A damaged trap or loose waste joint can let odours escape into a room. A blockage can trap organic material, while a defect in drainage or ventilation may affect multiple fixtures. A surface clean may mask an odour briefly without addressing its cause.

If the smell is persistent, associated with slow drainage, or present at several outlets, a plumber can inspect accessible traps and connections and advise whether a drainage specialist is needed. TraceFix serves Birmingham and London for plumbing leak and drainage-related investigations.