Why does my bathroom smell like sewage? Adelaide Plumber 

It’s all in the pipes. Plumbing is generally all connected and to answer this question, it helps to understand how your bathroom pipes are connected and how it all works.

The U-shaped pipe under your sink runs to a larger waste water pipe in the wall, called the P trap. One end of the P trap runs down to your sewer or septic tank and the other end runs all the way up to the roof to let fresh air in and bad smells out. There is the same basic set up behind your walls or beneath your bathtub or shower.

The U-shape of the P trap collects a small amount of water which acts as a barrier against sewage odours. If all is running smoothly, that small amount of water should stay in the P trap after flushing the toilet, turning off the sink or emptying the bathtub. Any gases will flow undetected and out through the vent.

Usually it comes down to lack of use of your sink, tub or toilet. The water in the P trap evaporated if it hasn’t been used. Running some water will allow the P trap to fill up again. If that’s not working, professionals recommend pouring pink water-safe anti freeze down the drain.

If this doesn’t resolve the problem, check for any leaks in the P trap. Leaks are usually easy to find.

If the system isn’t running smoothly, the outcome could be more hazardous than just unpleasant. Methane is the largest cause of sewer smell other dangers include hydrogen sulphide, carbon dioxide, ammonia, nitrogen oxides and sulphur dioxide. This can be caused by the improper disposal of gasoline and chemicals down the drain. Physical side effects can be felt from these.

Of course keep your bathroom clean and sanitised and always keep your plumbing in check.