How to troubleshoot rotten egg smell in water heaters? What causes the problem with the rotten egg odor in hot water, how to check and how to avoid it? Is it harmful?
Hydrogen sulfide gas (H2S) is the reason for rotten egg odor in water heaters. It can be easily checked by smelling the water coming out of the cold and hot water tap. If the smell is coming from the hot water tap only, the problem is in the water heater.
A bacteria known as "Divibrio Sulfurcans" inside the heater's tank converts the sulfate into the hydrogen sulfide and makes the water smelly. The bacteria is non-toxic (except in extremely high concentration) but it can affect the taste and odor of the water.
Rotten egg odor caused by the sulfur bacteria can be found in any tank-type water heater or manufacturer; AO Smith, Kenmore, GE, Rheem, Bradford White and other. It is also found in the groundwater, distribution pipeline and well systems.
Hydrogen sulfide doesn't produce the bad smell only but is also related to corrosion of metal components in the heating system and black stains on the plumbing fixture.
The good thing is that the gas does not affect the quality of water but if it is present in higher concentration in the air it can be dangerous. The result of sulfur bacteria growth is also a slime, which eventually might clog the pipes, and the presence of the iron bacteria, which is related to "rusty hot water".
One of the easiest ways to eliminate the rotten egg odor in your gas or electric water heater is to flush the tank with the chlorine bleach solution or hydrogen peroxide, which is safer. Like with the shock-treatment in the pools, shock-chlorination is the simplest way to disinfect and remove the smelly water from your heater. If the tank water is heavily infected than several repetition should be done. Chlorination should be done properly, to remove the bacteria totally from the plumbing, tank, faucets and fittings, or the problem might return back.
If thinking about buying a new water heater, my recommendation is to check Rheem Marathon series as they utilize the plastic tanks, do not have the anode rods, so chances of getting the rotten egg smell caused inside the unit are reduced, and their warranty is lifetime.