Bathrooms and toilets are parts of the hygiene of our daily lives, and because of this they get a large number of things such as dead skin, hair, oils, human waste and saliva washed down them every day. Your plumbing thanks to things like p-traps and vents is designed in such a way that the bad smell of these human waste products and the smell of the sewer that the pipes are connected to don't travel back up the drain and into you house.
But occasionally, issues occur and these smells are able to make their way into your house. Not only is this smell revolting but the methane gas that is travelling up those pipes is flammable and bad for your health.
To understand what can potentially go wrong, it is important to understand the basics of how a standard plumbing system works. The standard system used in your bathroom is called a DWV or drain, waste and venting system. Water that flows from your sink or shower goes through what is referred to as a “p-trap” which has a small amount of water left in the bottom once draining is complete to essentially block the gasses from coming back out your drains and tubs. There is also a venting system which redirects all these gases to an outlet vent on your roof safely aware from the inside of your house.
One of the most common causes of bad smells can be that in an unused drain such as a second bathroom the water in the p-trap has evaporated, allowing gases back into the house. If you notice a bad smell coming out of a sink of shower in a second bathroom run the tap for a couple of minutes and let the water build back up in the p-trap. This simple task might just be enough to stop the smell.
But often there are much more complex reasons for the bad smell, such as a build-up of the grease and fats that come of your skin or even clumps of hair. These problems should not be attempted to be fixed yourself and using common repair tools like drain snakes and drain cleaning chemicals can cause more problems with your plumbing in the long run. It's best to call a plumber who uses non-destructive technology such as CCTV drain cameras and High Pressure Water Jetting to correctly diagnose and clear a blockage or build up and get everything flowing freely again.
If you notice a bad smell coming out of a sink, shower or bathtub unless you are an expert it's always best to call a plumber who can come out and inspect your systems and diagnose the causes of the problem. This will ensure that the health and safety of your home remains at the highest standard and you can continue to live your life without the fear of the sewer smell.