Problems
Shower drain smell: what causes it and how to fix it
Written by Martin, M24/7 Bathrooms
Last updated:
A sewage smell from the shower usually means a dry trap, a blocked waste or a leak you cannot see. Here is how to tell which, and what each fix involves.
A sewer smell in the bathroom that appears when the shower runs, or lingers after it, is telling you something specific. The drainage system is designed to seal itself with water, and the smell means that seal has failed or the pipework beyond it has.
This guide works through the causes in the order we check them. Some you can rule out yourself in minutes; others need the tray or the floor opened up. If the answer turns out to be a failing tray or waste, our shower installation service covers the repair and refit, and the quote form below reaches Martin directly.
The trap: the water seal that keeps smells out
Every shower waste has a trap, a U-shaped section that holds water and blocks air from the drains. If a shower is rarely used, that water evaporates and the smell comes straight up. Running the shower for a minute refills it, and if the smell disappears, that was the whole problem.
A trap can also lose its seal through a partial blockage that siphons the water out as it drains, or through a trap that was never the right depth for the run. If the smell returns within days of using the shower, the trap or the pipework around it needs a proper look.
Blockages and biofilm in the waste
Hair and soap scum build up in the waste and the trap, and the bacteria living in that build-up produce a musty, drains-like smell of their own. Lifting the waste cover and clearing what you can reach, then flushing with hot water, removes the mild cases.
A shower tray blocked further down the run behaves differently: drainage slows, the tray holds water, and the smell is stronger because waste water is sitting in the pipe. A plunger or a drain snake sometimes shifts it; a blockage that keeps returning usually means a section of pipe that needs cleaning or replacing properly.
Leaks you cannot see
The serious version of a shower drain smell is a waste or trap that leaks under the tray. Water escapes into the floor void, sits there and stagnates, and the smell rises through the smallest gap. By the time it smells, the floor around the waste may already be suffering.
The companion symptoms are a stain on the ceiling below, a tray that flexes or grout lines that stay dark and damp. The leaking shower guide covers the leak side, and the shower tray replacement guide explains what happens when the tray itself has to come out.
What a proper fix looks like
A lasting fix starts by identifying which cause you have, because the repair ranges from running the tap to lifting the tray. Where the tray or waste has to come out, the floor is dried and checked, the pipework is renewed or resealed, and the tray is refitted on a solid, level bed with a new sealed waste.
If your shower has started smelling and the simple checks have not cleared it, it is worth acting before the floor pays the price. Use the quote form below or call Martin to describe the symptoms.
Want a professional to handle it?
Get a quote from M24/7 Bathrooms.
Questions
Frequently asked
Why does my shower smell when I have not used it for a while?
The water in the trap has evaporated, removing the seal that blocks drain air. Run the shower for a minute to refill the trap. If the smell returns quickly despite regular use, the trap or pipework needs checking.
Can a blocked shower tray cause a sewage smell?
Yes. Hair and soap build-up traps waste water in the pipe, and the bacteria in it produce the smell. Clearing the accessible waste and flushing with hot water helps mild cases; recurring blockages need the pipework properly cleaned or renewed.
Is a shower drain smell a sign of a leak?
It can be. If the smell is accompanied by slow drainage, a ceiling stain below or a tray that moves underfoot, water may be escaping under the tray and stagnating in the floor void. That needs investigating promptly.
Will bleach or drain cleaner fix the smell?
They can clear biofilm and mild build-up, so they are worth trying first. They will not fix a dry trap that keeps siphoning, a damaged trap or a leaking waste, and heavy chemical use can damage older pipework.