You have just had a home inspector tell you the water in your home smell like rotten eggs? You have checked with the neighbors and they don’t seem to have the problem. What can you do about the smell? This problem can occur, when the metal anode rod, (cathodic protection device), combines with a waterborne sulfate reducing bacteria. The result of this chemical reaction is hydrogen sulfide. This is where the rotten egg smell comes from. Although the smell is a little, well maybe a lot, hard to get over, it is not harmful to consume.
There are a few potential solutions that can resolve this issue.
First, you can try replacing the metal anode rod with a new one. If your anode rod is magnesium, try using an aluminum one if available. Aluminum anode rods will produce 30% less current, thus reducing the generation of hydrogen gas. There will still be enough current to protect the glass liner of your water heater.
Secondly, determine the source of the sulfate reducing bacteria and eliminate it. The sulfate reducing bacteria can be introduced into your water heater via soil contaminated water supply lines. As the supply line flushes out, the contaminant can end up in the bottom of your water heater. Thorough flushing of your water heater should solve the problem, (unless of course it is re-contaminated). First, shut off the water supply to your water heater and drain using the drain at the bottom of the unit. You should get some sediment, etc. You may want to refill and drain again to get rid of any remaining sediment. Second, add a quarter cup of chlorine bleach per 10 gallons of water and refill your water heater. Open all hot water taps and allow the solution to flow through the pipes until you smell the chlorine exiting from the taps. Let the solution sit in the water heater for approximately 1 hour. Again, shut off the water supply and drain the water heater using the drain at the bottom of the unit. Opening the hot water taps will allow all chlorine solution to drain back to the water heater. Fill the water heater a third time, flush the hot water lines, and drain again. Finally, fill your water heater and flush the lines a final time.
This should do the trick, and the rotten egg smell should be gone. The hydrogen gas produced by your anode rod, without the presence of the sulfate reducing bacteria is not a problem and will go unnoticed. If the sulfate reducing bacteria is re-introduced, the smell will return. If this happens, you should have your water source analyzed to determine if it is the source of the bacteria.