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 the 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.
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 are non-toxic (except in extremely high concentration) but it can affect the taste and odor of 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 only the 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 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".
Make sure that the anode rod is not extremely depleted. One of the recommendations regarding the rotten egg odor is to replace the anode rod. Most of the water heaters are equipped with the magnesium rods, but if you replace it with the zinc alloy rod you will significantly reduce the production of hydrogen sulfide gas while still protecting the metal tank effectively.
Make sure to avoid long periods of an inactive heater. Bacteria that produce the rotten egg odor likes the warm environment inside the tank with no water movement and if there is lack of the oxygen. One of the recommendations from the manufacturers and plumbers is to keep the temperature of hot water high enough (160 F) for a few hours and that will reduce the level of sulfur bacteria or remove it.
Keep in mind that bacteria that causes the rotten egg smell can enter your home plumbing system through the distribution system and well water.
Water softeners that are used to treat the hard water and reduce the sediment build-up are increasing the chances of getting the rotten egg smell, as they speed up the process of the anode rod depletion.
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.
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 the lifetime.