What's that sewer smell in my bathroom?

Concerns & risks

You walk into the bathroom and it smells like a sewer. There's no clog, no leak, just a stink that comes and goes.

Bad smells make the room unusable and you worry about a bigger plumbing problem.

Causes & evidence

Every drain has a water-filled bend (trap) that blocks sewer gas. If the water evaporates, gas comes up. Rarely used drains dry out first.

What to do

1. Run water in every drain for 30 seconds, including floor drains and the guest shower.
2. For rarely used drains, add a spoon of mineral oil after the water to slow evaporation.
3. Check the toilet base: a rocking toilet or a gap may mean a failed wax ring.
4. Clean the drain itself; biofilm in shower drains can smell too.

Common mistakes: People spray air freshener and move on. The cause is often a dry trap or a vent issue, so fix the source. Don't forget rarely used sinks, showers or floor drains. Pour water in them. If the smell is strong with gurgling drains, a plumber should check the venting and sewer line.

Speed Man tip: Smell persists with full traps? A vent problem or damaged seal needs a plumber.

Wrap-up: Sewer smell usually means a dried-out drain trap. Run water in every drain to refill traps. Persistent smell can mean a wax ring or vent problem.