By Vern Merryman, McCleary Wastewater and Water System Operator
Hot water odor problems? A water heater provides perfect conditions for creating hydrogen sulfide gas and can do it in a couple of ways. First, the warm environment is ideal for sulfur bacteria. Second, a chemical reaction between sulfate in the water and the water heater's magnesium anode rod can create hydrogen sulfide gas. Magnesium anode rods are standard in most water heaters and sulfate is a naturally occurring compound found in most groundwater. The magnesium supplies electrons that aid in the conversion of sulfate to hydrogen sulfide gas.
The first step is to replace the magnesium anode rod with one that is made of aluminum or an aluminum-zinc alloy. Aluminum and aluminum-zinc alloy rods don't contribute to the production of hydrogen gas. Don't remove the offending rod without installing a new one. The anode rod is designed to corrode so the tank and fittings do not. You will void the water heater's warranty if you simply remove the rod. Replacement rods sell for around $20 at plumbing supply stores. You won't find them at home centers.
To remove the old rod, shut off the water supply to the water heater and drain about 5 gallons of water from the tank so that water doesn't run everywhere when you remove the anode rod. It's best to drain the water through the drain valve at the bottom of the water heater because you will also remove sediment that collects inside the bottom of the tank. Sediment is another good breeding ground for bacteria. The water from the tank is very hot, so use caution. When you install the new rod, wrap some Teflon tape around the threads to make it easier to remove next time. Anode rods last anywhere from two to five years, depending on your water hardness. Check the rod every couple of years and replace it when the center core wire shows.
You also need to treat the inside of the tank. The most effective way to fight the anaerobic bacteria is to oxygenate the water with hydrogen peroxide. Anaerobic bacteria thrive where there is little or no oxygen. The hydrogen peroxide bubbles and charges the system, creating a harsh oxygenated environment. Pour in one pint of hydrogen peroxide per 40 gallons of tank capacity. This weak concentration is not harmful to you, but it will kill the bacteria. Install the new anode rod, turn on the water supply and refill the tank. Run all the hot water taps until they are hot and then turn them off. It's important to get the oxygenated hot water to the end of every hot water line.
Let the treated water stand for two to four hours. Then run each hot water tap for about five minutes to flush the peroxide. This also drains enough hot water from the water tank to clear the system. Don't expect this to be a one-time cure; a water heater may need to be oxygenated three or four times in one year. It is unlikely that you will kill all of the bacteria in one treatment. For more information, please give me a call at 495-3217.