Sulfur or Rotten Egg Smell

This odor may indicate bacteria growth. This could be in your drain. Over time organic matter (such as hair, soap, and food waste) accumulates on the walls of the drain. Bacteria grow on these deposits and emit gases with the odor. When you turn on your faucet, the force of the water going down the drain pushes these gases up into the air where you will smell them. Disinfecting the drain with bleach should eliminate the problem. If this doesn't eliminate the problem, or if you notice the odor in more than one place in your home, the bacteria could be growing in your hot water heater. Turn the temperature of the hot water heater up very high for a short period of time. This will kill any bacteria growing in the hot water heater.

If your hot water heater has a magnesium rod to prevent corrosion of the heater, the odor could be caused by sulfur reacting with the magnesium. Contact the company that installed the hot water heater to inquire about either replacing the magnesium rod with an aluminum rod or having the rod removed (note that removing the rod may void the heater's warranty).