We like to think of our bathrooms as a peaceful, spa-like escape. But that’s impossible to do if a foul odor is coming out of your bathtub drain. If you have to hold your nose as you bathe, then this article is ideal for you. Here are the two most frequent causes of a smelly shower drain — and what you can do in order to solve the issue.

Reason #1: Problem using the P-trap

If you can look underneath the shower drain, you will see a U-shaped pipe that water passes through. This is called a P-trap, and the purpose is to maintain a small amount of water at all times to prevent sewage gasses from coming back up the pipe and in your bathroom.

If you haven’t used the shower in a little time, then it is very likely that the water at the P-trap has evaporated. This is an easy fix — just run water from the shower for a few minutes and the P-trap will refill and the smell should go away.

But if you have utilized the shower lately, it may be a indication that there’s a leak at the P-trap. If that’s the case, the pipe needs to be replaced to resolve the odor and prevent further water damage in your home.

Reason #2: Buildup of biofilm

Biofilm is a thin, slimy layer of bacteria that can grow from all the water, soap, shampoo, and body oils that go down the shower drain and accumulate inside the pipes. Not only does this sound gross, but it can also smell quite bad.

So how can you get rid of biofilm? You can try killing the bacteria with these household solutions:

Mix 1 part bleach and one part water, then pour down the drain.

First, pour one cup of baking soda down the drain. Then add a cup of white vinegar. Cover the drain as the mixture fizzes, then flush with hot water.

If hair gets trapped in the drain or pipes, it can make the biofilm issue even worse (not to mention start a clog). Often, if you can eliminate the hair, then the odor will go away.