Q: Hi Steve, occasionally we get strong sewer fumes that seem to come from the basement bathroom. Any ideas what this could be? Any insight would be most appreciated.

Thanks, Ann

A: First thing that comes to mind is a dry shower drain. You said the bathroom would be used only for TV room use– if the shower hasn’t been used for a while, start there. When water in the drain’s p-trap evaporates, it allows sewer gases into the home.

All sewer drains have a p-trap = the U shaped drainpipe fitting we see below our sinks. These are intended to hold water and block the sewer odors from entering our homes. Toilets have them built-in, floor drains, showers and bath tubs have them below the floor level.

My guess is the shower is rarely used and the drain has dried out. (This can happen even faster in warm weather). Pouring a couple cups of water into the drain should re-charge the trap and block the smell. Keep in mind that all unused plumbing fixtures can create this same experience. The forgotten wet bar, the unused basement floor drain, or the unused washing machine drain connection…

A little bit of water should clear the air.

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