Few things make you back away from a faucet faster than the smell of rotten eggs in your hot water. It is unpleasant, but it is rarely dangerous, and it is almost always fixable once you understand what is happening.
What Causes the Smell
That sulfur odor comes from hydrogen sulfide gas, produced when naturally occurring sulfate in water reacts with bacteria inside the tank. The reaction is often accelerated by the magnesium anode rod, which is doing its job protecting your tank but can feed the bacteria in the process.
A quick test: if the smell is only in the hot water, the water heater is the source. If both hot and cold smell, the issue is your water supply, and a different fix is needed.
The Common Fixes
- Flush the tank. Clearing out sediment and stagnant water removes the environment bacteria love. This is the first step and sometimes the only one needed.
- Replace the anode rod. Swapping a standard magnesium rod for an aluminum-zinc rod often stops the reaction that produces the odor. This is a common and effective fix.
- Disinfect the tank. A controlled chlorine treatment can kill the bacteria causing the smell, especially on well systems.
- Raise the temperature briefly. Bacteria struggle at higher temperatures, though this should be done carefully to avoid a scalding risk.
Why It Comes Back
If you only mask the smell without addressing the anode rod or bacteria, it tends to return. The lasting fix is usually the rod swap plus a good flush, which removes both the fuel and the environment for the reaction.
When to Call Us
If a flush does not solve it, or you are not comfortable pulling the anode rod, we can diagnose the exact cause and fix it in one visit. Rotten-egg smell is a common call for us across Mount Pleasant and Charleston, and it is very solvable.