How to troubleshoot rotten egg smell in water heaters? What causes the rotten egg odor in hot water, how to diagnose and get rid of the smell? Is it harmful?
Hydrogen sulfide gas (H2S) and anaerobic bacteria, combined with the standing hot water inside the tank, are the main reasons for the rotten egg odor in hot water and water heaters.
The 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 water.
Except for the water heaters, the sulfur odor can also develop in corroded iron piping, even if the incoming city water is chlorinated. This occurs when water was stored and inactive for several days, the concentration of chlorine is low and level of sulfates high.
It is easy to diagnose the problem 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.
Rotten egg odor caused by the sulfur bacteria can be found in any tank-type water heater no matter of the manufacturer; AO Smith, Kenmore, GE, Rheem, Bradford White or any other. It is also found in the groundwater, distribution pipeline, and well systems.
Hydrogen sulfide doesn't produce only bad smell but is also related to corrosion of metal components in the heating system and black stains on the plumbing fixtures.
The good thing is that the hydrogen gas does not affect the quality of water, but if it is present in higher concentration in the air it can be dangerous.
The sulfur bacteria growth can also develop slime, which can clog the pipes, while the presence of iron bacteria, could lead to rusty hot water.
One of the easiest ways to eliminate the rotten egg odor from your gas or electric water heater is to flush the tank with the chlorine bleach solution, or if you are looking for a safer option - hydrogen peroxide. Like with the shock-treatment of 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 repetitions should be done. To remove the bacteria totally from the plumbing, tank, faucets, and fittings, chlorination should be done properly or the problem might return back.
Rotten egg odor is not harmful but is irritating. The Sulphur smell is a common problem in many households, hard to remove but when done correctly could save you lots of money.
If thinking about buying a new water heater, my recommendation is to check Rheem Marathon series as they utilize the plastic tanks, do not use anode rods, so chances of getting the rotten egg smell are minimal, and the warranty is a lifetime. You can also buy a tankless which heats water on demand resulting in fresh hot water delivery. It does not store water and does not utilize the anode, which are the main reasons for the rotten egg problem.
Please describe the problem in details including the type of water heater and brand/model.