If you smell an odor like rotten eggs coming from your water heater, you may have sediment built up inside of it. Below is information on how you can remove this sediment to get rid of the smell.
Cleaning and Sanitizing
Before you begin, refer to the water heater user's manual so you know where the parts below are located.
If your water heater is electric, turn off the manual switch before you begin. If your water heater is gas-powered, turn the control to pilot. This pilot should stay lit, which will allow you to turn the water heater back on when you finish cleaning it.
Close the cold-water inlet valve on the water heater, and open a hot water faucet that is near the water heater. Lift the lever on the temperature and pressure valve to open it. You will find this on top of your water heater. This releases the tank pressure. Drain three pints of water from the water heater by connecting a hose to the drain valve.
Add the Hydrogen Peroxide
Purchase some three-percent hydrogen peroxide, which can be found at most drugstores. Determine the capacity of your water heater. If your tank has a 40-gallon capacity, add two pints of peroxide to the water. If your water heater tank holds 80 gallons, add four pints, and so on. You can pour the peroxide into the tank through the temperature and pressure valve opening.
Open the cold water inlet on the water heater, and let it fill the tank up with water. You will know it is full when water runs out of the nearest faucet. When it is full, close the valve, and leave the hydrogen peroxide in the water heater for three hours.
After three hours, open the cold valve, and all hot water heater faucets. This will let the hydrogen peroxide clean the supply lines. Close the drain valve and fill the water heater with water, and leave it in for 20 minutes.
After 20 minutes, open the drain valve to purge the water supply lines, and drain the water from the tank. Open a hot water faucet to remove any air that may be in the hot water lines. Open the cold water inlet to refill the hot water heater with water.
The smell from your hot water heater should now be gone. If it is not, you should contact a plumber at http://www.rakeman.com/, because you may be having other problems.