First, figure out where the smell is: run the cold and hot taps separately. The Minnesota Department of Health recommends this step, because a smell on both sides points to the water supply, not the heater.
Why it happens
A.O. Smith explains that four things must be present: sulfate in the water, little dissolved oxygen, sulfate-reducing bacteria in the heater (which it describes as nontoxic to humans), and excess hydrogen produced by the anode's protective action.
The fix manufacturers recommend
- Replace the anode with one of a less active material (Bradford White recommends its A420 anode).
- Chlorinate the tank and hot water lines.
- Do not simply remove the anode: A.O. Smith says that voids the tank warranty, and Bradford White says it shortens tank life.
Who should do it
The Minnesota Department of Health advises having a plumber do the work unless you are experienced, and warns that raising the heater temperature to kill bacteria can be dangerous. The Wisconsin DNR notes that switching anode material reduces the bacteria but may not eliminate them.
Common questions
Is the rotten egg smell dangerous?
A.O. Smith describes the bacteria involved as nontoxic to humans, but the smell is unpleasant and worth fixing. If you smell rotten eggs near a gas appliance rather than in the water, treat it as a possible gas leak and leave the house.
General information, not professional or legal advice; follow your manufacturer's manual, and your installer and local permit office have the final word. Sources:A.O. Smith residential electric water heater manual (185762); Bradford White, Hydrogen sulfide odor and chlorinating water heaters; Minnesota Department of Health, Hydrogen sulfide in well water; Wisconsin DNR, Water smells like rotten eggs.
Water Heater Repair in San Diego →