How do you fix a smelly bathroom drain?

[#1]

A water trap has been positioned somewhere in your plumbing layout to keep sewer gas from entering your home. If you've not been using your bath for a certain amount of time the water inside the trap might have evaporated to a lower level. If it goes past the trap point the sewer gas will be able to pass through the air gap in the trap and enter your room. Please have a look at the diagram below.

I suggest tipping in a bucket full of water into the bath waste to restore the water level in the trap. To clean out the smell in the pipework, I propose tipping in a cup of baking soda into the bath waste, please use a paper funnel to make sure it all goes into the waste and not on your tub. Then tip in a cup of cleaning vinegar, there will be an immediate fizzing reaction, cover your bath waste with the bath plug. Wait for 10 minutes and then run hot water into the drain.

I also suggest tipping in a bucket of water in your floor drain as a secondary trap might be positioned further along. Open your doors and windows to promote air circulation. Unfortunately, sewer gas smell has a tendency to stick to objects, I suggest having a look at Peerless JAL 750ml Attack Odour Neutraliser to help get rid of the smell.

Please make sure to wear proper safety equipment such as disposable gloves and safety goggles when mixing the baking soda and cleaning vinegar. - EricL

[jayell]

Eric's well writen and descriptive response is most likely correct, but there is a small chance that it may be a venting issue. If there is no vent on this line or the vent is blocked then a vacuum caused by waste flowing down the drain can sometimes suck the water from the trap. 

If the smell comes back within short period you should get a plumber to check the venting.

[EricL]

Hello @jayell 

Welcome to the Bunnings Workshop community. It's sensational to have you join us. 

Thank you so much for sharing your knowledge and experience in regards to smelly bathroom drains. I believe it's among the most common complaints from homeowners who have encountered this type of problem. Any extra information on possible solutions is always appreciated.

Were keen to hear more about all your projects and plans around the house and garden. Please feel free to reach out whenever you need assistance or would like to share a project with the community.

Eric