Your shower is supposed to smell fresh and clean. If a bad smell is coming up from the shower drain, not only is showering less inviting, but you could have a serious plumbing issue on your hands. Do not ignore a shower drain smell; if the odour is caused by sewer gas, repeated exposure could lead to health problems.
Two main types of smell drift up out of a shower drain. The first is a rotten, bacterial odour. It usually occurs in conjunction with a shower drain that drains very slowly or is completely clogged. The smell will be present all the time. The other odour is the terrible smell of sewer gas. This usually occurs in a shower in a guest bathroom where the shower is not often used. The smell disappears after you run the shower, but once the shower stops being used for a month or two, the odour will return.
The cause of the spoiled, rotten smell is a clog in the shower drain, usually caused by hair caught inside the drainpipe. The hair traps organic material as water runs down the drain. Over time, the organic material attracts bacteria and emits a bad smell. The clog also causes the drain to empty slowly. The odour of sewer gas occurs when sewer gas drifts up the drainpipe and into your home. Your shower drain is a curved pipe with one bend that should always be filled with water. Known as a trap, the water-filled bend seals the drainpipe and keeps sewer gas out of your home. If a shower goes unused, the water in the trap can evaporate, removing that barrier.
Removing the clog from your shower drain will get rid of the rotten smell. Plunge the drain to force the clog loose and down the drainpipe. If that does not work, create a drain cleaning solution by pouring 1/4 cup of baking soda down the drain, followed by 1/2 cup of vinegar. Once the fizzing stops, run water down the drain. To get rid of the odour of sewer gas, run water in the shower for about 20 seconds. This will refill the trap and block the sewer gas. Run water into the drainpipe every month or so to keep the trap full.
Installing a sieve in your shower drain will catch hair and prevent it from getting into the drainpipe, which will reduce the risk of clogs occurring in the future and causing the bacterial smell to return. If the odour of sewer gas occurs in a shower that is used often, changes in pressure in your plumbing pipes could be siphoning water out of the trap. Run water down the drain daily to keep the trap full. If you notice the smell coming from other drains in your home, contact a plumbing professional. Sewer gas entering your home from multiple points could signal a more serious plumbing issue.