Water Heaters - Smelly hot water - won't go away

For about a year, we have been experiencing an unpleasant problem with our hot water. It has a horrible sulfur odor and a gray sediment. I flushed the water heater several times, but the problem didn't go away. We then decided that the water heater needed replacing anyways, so I did that. The odor and the sediment went away briefly. Now it is just as bad as before.

To make things more difficult to diagnose, this is happening on one side of a duplex, but not the other. Both sides share a common city water supply, and the water passes through a common water softener before it is split between the two sides of the house (and the two separate water heaters). :wall:

Rotten egg odor may be due to hydrogen sulfide (H2S) gas. If it is in hot water only, then the blame is usually the water heater because the warm environment makes it possible for sulfate-reducing bacteria to live. Magnesium anodes suppy electrons that sustain the reaction of sulfate to the gas. If odor seems to dissipate after water runs then the bacteria could be in the hot water pipes.

If the problem is the water heater, remove or replace the magnesium anode if you have one. Disinfect and flush the water heater with a bleach solution or increase the water temperature to 160 degrees Fahrenheit for several hours to kill the bacteria, then flush the heater.

If odor is in both hot and cold, then bacteria could be in water softener. Contact manufacturer for instructions on disinfecting it.

Before proceeding have water tested.