How to Treat Sulfur Water and Reduce the Rotten Egg Odor


The term “sulfur water” typically refers to water that has a rotten-egg odor that is caused by hydrogen sulfide. When treating water to remove the odor, we need to determine the potential source of the hydrogen sulfide:

  1. Odor on hot side only. If the sulfur odor occurs only in the hot water, the most likely source is a reaction between an anode rod in the water heater and natural sulfate ions in the water. An anode rod is made from magnesium or aluminum, and its purpose is to protect the steel water heater tank from corrosion. Magnesium rods are more likely to cause the odor, so the first step would be to replace the magnesium rod with an aluminum rod, if available. If the aluminum rod still produces the odor, the next step would be either to operate the water heater without an anode rod or to remove the sulfate ions.

    Removing the anode rod would remove its corrosion protection, potentially shortening the life of the water heater tank. There are FDA-listed corrosion inhibitors we can add to the water to extend the life of the tank.

  2. Odor in the cold water that goes away after water flows. In this scenario, the most likely source of the hydrogen sulfide is Sulfate-Reducing Bacteria (SRB’s). The bacteria are not considered pathogenic, but the “breathe in” sulfate ions and “breathe out” hydrogen sulfide, just like we breathe in oxygen and breathe out carbon dioxide. Just like an un-ventilated room full of people can get stuffy after awhile, a section of plumbing where there is no flow can get stinky after a while when SRB’s are present. Therefore, a characteristic of a rotten-egg odor due to SRB’s would be a strong odor in the cold water at first draw (for example, filling the pot for morning coffee), with the odor decreasing as the cold water flows.

    Active sulfur-reducing bacteria can be located anywhere within the plumbing system, well casing or in the aquifer. Many laboratories conclude that sulfur reducing bacteria are present if the water tests positive for coliform bacteria and has a "rotten egg" smell. If well water has a rotten egg smell due to sulfur reducing bacteria, shock chlorination can eliminate the problem but will not eliminate the source. Sunaqua will Place a single high dose of chlorine (5.25 percent hypochlorite) in the well, distribution lines and within the plumbing system, allow 12 to 24 hours contact time for the chlorine to kill the bacteria, and finally flush the added chlorine out. The concentration of chlorine used in shock chlorination is 100 to 400 times higher than the amount found in treated "city water." If the concentration and contact time are adequate, chlorine is an excellent disinfectant that kills most disease-causing bacteria, viruses and cysts of protozoa as well as iron, manganese and sulfur bacteria. Occasionally, iron and sulfur bacteria are difficult to kill because they occur in thick layers and are protected by a slimy secretion. If multiple attempts of shock chlorination fail to control or eliminate the hydrogen sulfide problem, continuous chlorination or other methods may be required. for more information on systems that will remove Sulfur Reducing Bacteria visit

  3. Odor in the hot and cold water that does not decrease as the water flows. This is true hydrogen sulfide from the source aquifer. There are a number of treatment methods available, including a Softener system, a KDF filtration system or AIO iron filter, or chlorine for water with P.H of 7.5 or less hydrogen peroxide for water with 7.6 or higher P.H and carbon filtration. The choice will depend on the level of hydrogen sulfide and other contaminants (like iron) in the water as well as the peak flow rate (gallons per minute) and the peak daily water usage (gallons per day).

As with many water problems, the cause may be complex and require in-depth exploration. For hydrogen sulfide, that exploration starts with finding the source.

If you are concerned you have hydrogen sulfide in your water, contact Sunaqua. We will be able to perform a water test to determine what is in your water and suggest the perfect water treatment solution for you. We are specialized in water well systems and there specific conditioning needs.