Why your shower trap smells – and how to solve it

Our bathrooms should be a peaceful, spa-like escape. However, if you've noticed a foul smell coming from your shower drain, there could be a simple explanation. To help you find the culprit of your shower drain smells, we've created this handy guide to get your bathroom back to looking – and smelling – fresh!

Problem with the P-trap

One of the most common issues is a problem with the P-trap. You may find that if your bathroom smells like a sewer after a shower, the P-trap is the culprit. If you can look underneath your shower drain, you'll see a U-shaped pipe that the water passes through. This is the P-trap. The purpose is to hold a small amount of water at all times to block sewage gases from coming back up the pipe and into your bathroom.
If you haven't used your shower in a while, it's possible the water has evaporated. Simply run water in the shower for a few minutes and the P-trap will refill. You can also mix water with a touch of ZoFlora to add a pleasant aroma – perfect for guest bathrooms.
However, if you have used your shower recently, it could be a sign there's a leak in the P-trap. In this case, the pipe needs to be replaced. This will help resolve the smell and prevent further water damage in your home.

Build-up of biofilm

Biofilm is a thin, slimy layer of bacteria that can grow from all the water, soap, shampoos, and body oils that go down the drain. This can then accumulate inside the pipes, causing your shower drain to smell like rotten eggs.
To get rid of the odour – and the build-up – you can mix 1 part bleach with 1 part water and pour it down the drain. Alternatively, you can pour 1 cup of baking soda down the drain, followed by one cup of white wine vinegar. Cover the drain as the mixture fizzes, then flush with hot water.
If hair gets stuck in the drain or pipes, it can make the biofilm even worse. Adding a hair trap can help stop the build-up of biofilm.


If your shower drain smells musty, you may have mould growing underneath your drain cover. Feel the drain cover to see if it's loose. If your drain cover isn't perfectly sealed, that small wet space will be the perfect breeding ground for mould.
Before sealing it, you'll need to remove the cover and clean the area thoroughly. Using a mould spray and following the instructions will help clear the mould and the smell. If it's really bad, you may need to scrub the cover too! If this doesn’t solve the issue, you may need to buy a new drain cover.

Leaky pipes

If water is draining away okay and you've checked to make sure the pipes aren't clogged with hair or biofilm but your shower drain still smells, it may be that you have leaky pipes. Leaky pipes in your bathroom walls or under the shower will allow sewer gases – hydrogen sulphide – to escape, causing your shower drain to smell like rotten eggs.
Drainage pipes are designed to keep sewer gases contained, and if it's not coming from the P-trap then you have a leak somewhere in your drain line.
Leaks are caused by either perforations in the pipes or by loose fittings between pipe joints. Often leaky pipes occur over time due to corrosion. Fixing a leaky pipe is best left to the professionals, so calling in a plumber is a must. A plumber should be able to fix the issue, so you can go back to breathing easy in your bathroom.
If your bathroom woes extend beyond the shower drain smells, it might be time for a complete makeover. You can easily make your bathroom the most important room in the house with our help. Whether you're looking to create a sleek and stylish space or your style is more traditional, we have a bathroom suite for you.
Download our latest brochure today for more bathroom inspiration or book a virtual design appointment today.