There are certain questions a home inspector frequently gets regarding the water heater. One question is, “Why do I have a ‘rotten egg smell’ coming from the hot water tap?” To understand the problem you must understand the mechanics. In the top of the tank is the anode rod.
This rod is a metal rod consisting of magnesium and sometimes aluminum. These metals help protect the water tank from corroding because electrolysis eats away at this rod rather than the metal tank itself. However, bacteria can react with the decaying magnesium anode rod causing the formation of hydrogen sulfide hence, the rotten egg smell. The cure for “rotten egg smell” is achieved by replace the magnesium anode rod with an aluminum rod.