Smelly Hot Water

It is common for cold water with a high sulfate content to transform from odor free to obnoxiously smelly after passing through the hot water heater. Typically the sulfates react with the magnesium (and even the aluminum) anode rod to chemically reduce the sulfate to sulfide. It is also speculated the smell may be the magnesium rod reacting with naturally occurring anaerobic bacteria creating hydrogen sulfide gas. To rectify the problem the magnesium rod needs to be replaced with an anode rod comprised of an aluminum/zinc alloy rod. This specialty anode rod is less reactive with the sulfate thus eliminating the reduction reaction. The cost for a typical 39” anode rod is $70.00. It is important to sanitize the hot water heater with hydrogen peroxide or chlorine at the time of anode rod replacement.

 

Sacrificial anode rods are used to protect the steel body of the hot water tank. When two metals are present in water electrolysis occurs. The less noble/stable metal will corrode while the more stable will remain in tact. When steel and copper are together as in most plumbing systems the steel is less noble and will corrode. To protect the hot water heater a sacrificial anode rod is an integral part of the design. The anode rod is typically comprised of magnesium or a combination of aluminum/zinc. These metals will sacrifice themselves leaving the steel water heater in tact. To remain useful the rod should be changed approximately every five years.

 

John Crean

Certified Water Specialist