A magnesium anode rod is typically installed in which appliance?

• A. Tankless Water Heater
• B. Boiler
• C. Water Softener
• D. Storage Type Water Heater

Answer: (D)

Magnesium anode rods are used to protect the steel interior of a storage-type water heater by acting as a sacrificial metal. They’re installed in the hot water tank because that tank is a large steel vessel that sits in contact with potable water for many years, making it susceptible to galvanic corrosion. The magnesium rod preferentially corrodes instead of the steel lining, slowing tank deterioration and extending its life.

Tankless systems don’t have a storage tank to protect, so they don’t use a sacrificial anode rod. Boilers and water softeners aren’t designed with a protected steel water storage tank in mind, so a magnesium anode rod isn’t used there in the standard sense. That’s why the magnesium rod you’d typically install is in a storage-type water heater. Over time the rod dissolves and should be replaced to maintain tank protection.