Rotten egg and sewage smells are an indication that you have a serious bacteria problem in your sink drain. Bacteria grow and develop in the bits of food, soap and other debris in your drain. People usually associate the nasty smells with the water because the smells appear when the water is turned on. The source of the smell is actually the gases produced by the bacteria. The gases are pushed upward when the water is turned on. Disinfecting a drain is an easy procedure that can be done with regular household bleach
Turn on the cold water and let it run down the drain for 15 seconds.
Pour 2 cups of chlorine bleach into the drain. Protect your hands with latex gloves. Pour the bleach around the edges of the drain so that it runs down the sides of the drain. Allow the bleach to stay in the drain for 10 minutes.
Turn on the hot water and flush the drain for one to two minutes. If the drain has a garbage disposal turn the garbage disposal on while you are flushing the drain. Turn the hot water off. Wait a few minutes and turn the cold water on. Repeat the procedure If the rotten egg smell is still present.
Disinfect the drain twice a week. Pour 1 tbsp. of chlorine bleach mixed with 1 quart of water down the drain to prevent bacteria from developing.