By Paul Bianchina
Q: Can you tell me why my shower drain has an odor after running water in it? -Kay D.
A: There are two things I'm aware of that can cause this, depending on how often the shower is used.
If the shower is used only infrequently, the water in the trap below the drain can evaporate. When this happens, there is no longer a seal in the trap and sewer gasses can come up through the drain, either on their own or as soon as water first enters the drain. To prevent this from happening, you need to make sure the trap never dries out, which can be done by either periodically running water in the shower, or by having a plumber install a trap primer, which is a small water line that will trickle a small amount of water into the trap as needed.
If the shower is used frequently and you don't feel that the trap ever dries out, then the problem is probably coming from debris - dirt, hair, soap, etc. - that is lodged in the trap and either rotting or mildewing. If the trap is removable from under the house, simply place a bucket under the trap, undo the nuts holding the trap in place, and slip the trap off the drain line. You can then clean out the trap with a garden hose, bottle brush, or other means. Soaking it overnight in a solution of 1 or two parts household bleach to 10 parts water will also help.
If the trap is not removable, you can try any of the gel-type drain cleaners on the market - carefully follow the manufacturer's instructions, and repeat as needed until the drain is completely clear - or you can have the drain and trap professionally snaked out. Check the Yellow Pages under "plumbing drains and sewer cleaning." I am assuming that this is only coming from one shower. If it is coming from more than one shower, then the main drain line may need to be snaked out as well.
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