The smell coming from a shower drain is usually caused by one or more of the following issues:
- Clog buildup: Dirt, grime, hair, soap scum, and other debris accumulate over time, trapping bacteria that produce foul odors which then escape through the drain.
- Dirty or clogged P-trap: The P-trap is a U-shaped pipe under the shower that holds water to block sewer gases. If it gets clogged with debris or dries out due to infrequent use or ventilation problems, gases can escape and cause the smell.
- Biofilm buildup: A slimy layer of bacteria grows inside the drain and pipes from organic materials like soap and body oils. This biofilm emits unpleasant odors.
- Mold growth: Mold can develop beneath the drain cover or in moist, poorly sealed areas, causing musty smells.
- Leaky or damaged drain pipes: If pipes have leaks, sewer gases can escape into the bathroom, causing a rotten egg or sewage smell.
To fix the smell, common approaches include running water to refill the P-trap, cleaning out clogs and biofilm with baking soda, vinegar, bleach, or specialized drain brushes, removing and cleaning the drain cover to eliminate mold, and calling a plumber if leaks or ventilation issues are suspected.
In summary, a smelly shower drain is mostly caused by clogged debris, P-trap issues, bacterial biofilm, mold, or pipe leaks allowing sewer gases to escape into the bathroom.
