Sometimes drains and pipes just smell for no determinable reason. Other times, the smell is a result of a clogged shower drain, or stagnant water in the bottom of the drain. Besides dealing with the cause, you also need to get rid of the smell itself. After removing the drain trap, or clearing the clog you can begin taking steps to remove the smell from the drain.
Pour 1 gallon of boiling water slowly down the drain. This will flush the drain and loosen any growth or bacterial that may be causing the smell.
Sprinkle 1 cup of baking soda into the drain and allow it to sit for 30 minutes. Baking soda absorbs odours.
Add 3 cups of white vinegar slowly down the drain. You will hear the fizzing as it interacts with the baking soda. This process will kill bacteria and germs in the drain as well as cleaning sludge from the inside of the drain pipe.
Leave the vinegar and baking soda in the drain until you take a shower again. The longer it has to work in the drain area of the shower, the better it will take care of the smell. It will also help clear away the stuff that can cause future odours.
Repeat this process monthly to help keep your shower drain clean and smell free.