Why does my shower drain smell like sewer?

Start with the trap

North Dakota's environmental quality department says sewer gas in a home is usually caused by leaks in plumbing or a dry trap in a rarely used drain. If the trap is dry, pour water down the drain to refill it (North Dakota DEQ). Guest showers and basement floor drains are the usual suspects.

If the trap is full

The same guidance suggests a cup of baking soda followed by a cup of vinegar, a few minutes of waiting and a hot water flush, then airing out the room with windows and exhaust fans (North Dakota DEQ). Avoid mixing different drain products. Poison Control warns that mixing some household cleaners, such as bleach with ammonia or acid, can produce toxic fumes (Poison Control).

When to call a plumber

North Dakota's guidance says to call a plumber if the smell is strong and widespread after cleaning, if you see cracked pipes or damaged fixtures, or if it keeps coming back (North Dakota DEQ). A plumber can check the trap, the drain seal and the vent pipe that lets the system breathe.

When it's a backup

ATL311 lists waste seepage around a shower drain, sink or basement drain, or being unable to flush toilet waste, as signs of a sewage backup inside the home. It asks Atlanta customers to call 404-546-0311 about a possible sewer spill (ATL311). If sewage reached the floor, see sewage cleanup in Atlanta.

Common questions

Is sewer gas dangerous?

Treat a strong smell seriously: air the room out and get the source found. If you smell gas that could be natural gas rather than sewer, leave and call the gas utility.

Why only one shower?

A drain that's rarely used is the classic dry-trap case (North Dakota DEQ). Running it every week or two usually keeps the smell away.