In addition to this, tank water heater systems include a sacrificial anode rod. Water heater tanks include different metals in contact with the water, which cr

In addition to this, tank water heater systems include a sacrificial anode rod. Water heater tanks include different metals in contact with the water, which creates a galvanic cell. Over time this corrodes the least noble metal. The rod is added in the design to corrode before pipes do. The rod is usually magnesium, aluminum or aluminum-zinc. It slowly but steadily leeches out the rod metal into the hot water supply.