Why does my toilet smell bad?

Updated February 21, 2017

If you regularly clean your toilet and still smell bad odours in the room, you might have plumbing problems. You may be able to fix the problem yourself or you may need to call a professional plumber. Some common problems include a build-up of biofilm and mould, and lack of water in plumbing fixture traps. With any of these problems, the odours of the decaying waste in the sewer or septic systems may be emitted though the toilet.

Not Enough Water in Traps

The drain lines beneath sinks, tubs and showers have P-shaped kinks that trap water. These traps retain water so that sewer gas and vermin can't travel up into your home. If you don't use the sink or shower much, the water in the trap sometimes evaporates. Pouring a quart of water in the drain can usually fill the trap and seal off the unwanted odours.

Slime Build-Up in Tailpipe

Slime can build up on the inside surface of bathroom drains. When it builds up on the tailpipe, which is the piece of pipe that extends from the bottom of the sink to the top of the P-trap, it releases unpleasant odours. Bacteria and dirt pass through the tailpipe and over time collect on the inside surface of the pipe. Because the pipe is exposed to the air in the bathroom, it causes odour problems. Removing the tailpipe and cleaning it may eliminate the odours.

Slime Build-Up in Overflow

The overflow is the hole at the top of the sink that connects to the bottom of the sink. Slime can also accumulate on the surfaces of the overflow, releasing unpleasant odours. If your bathroom is connected to a city sewer system, pouring a mixture containing equal parts chlorine bleach and water into the overflow hole may solve the problem. If you are on a septic system, cleaning the overflow with a bottle brush may remove the smell without harming the bacteria in your tank.

Plumbing Problem

If the other listed causes don't apply to your situation, you may need to call a professional plumber. If you smell sewer gas in your toilet, it may endanger your family. It contains methane gas, which is explosive and can reduce the oxygen level in the room. The seal of your toilet may have broken down or your vent pipe may have cracked. Other possibilities include clogging and improper plumbing installation.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Edriaan Koening began writing professionally in 2005, while studying toward her Bachelor of Arts in media and communications at the University of Melbourne. She has since written for several magazines and websites. Koening also holds a Master of Commerce in funds management and accounting from the University of New South Wales.