Hot Water Heater / Hydrogen Sulfide Odor

For private well owners and even city water or tap water customers, hydrogen sulfide / sulfide or rotten egg odors or odor problems with your drinking water.  If a Hydrogen Sulfide odor, rotten egg odor, or an off taste or other odor is associated primarily with the hot water system it may be necessary to pasteurize the hot water heating system and hot water lines or you may need to modify the hot water heater system to eliminate a condition that is creating the odor either chemically or biochemically. If your drinking water (well water or tap/ city water) has a sulfur like odor that is stronger or only present in the heated water, we recommend the following (pasteurize the water heating system):

• Turn off the system and drain the tank. Note any anomalies such as: the color and odor of the water, coatings, precipitates, or other solid materials while you are draining the water.

• Change or replace any water filters that are before or after the hot water heating system and when you replace the filters note if the filter is coated with a slimy material and if the material has a color.

• Allow the tank to refill, but raise the temperature setting of the tank to a level above 140 F.

• Allow the tank to stay at this level for at least 6 to 12 hours.  After the tank has been setting unused for 3 hours or so, send hot water through the piping to the various spigots.  Please remember to remove the aeration device and that the water is very hot.  
  

• We recommend that you start the spigot or faucet furthest away from the heating system. Purge the water until you notice the heated water.  (Note:  We recommend you do not use the hot water for cooking, cleaning, showering, or bathing at this time.)

• When the time period is up, turn off the hot water system and reduce the system to the normal temperature setting.

• Drain any discolored water and then allow the tank to refill.  Then flush all the hotwater lines to waste and reinstall the aeration devices. 

• If the odor goes away it was most likely bacteria growing (Slime forming bacteria / Sulfur reducing bacteria)  in the tank and or the water lines that was causing the problem.

If the odor returns immediately, it is likely a chemical reaction between the water and the Sacrificial Anode used in the water heating system.

It would be advisable to check the quality of the water entering the tank and check to make sure that all the backflow prevention devices are working properly. We strongly recommend a basic water quality testing depending on the source of the water (Well Water Testing / City Water Testing).

If you have a well, we recommend that you also Shock Disinfect and flush the well and distribution system.

If the pasteurization worked and your system has a magnesium sacrificial rod, it may be wise to replace the rod with an aluminum rod or  a power anode rod. The other options would include switching to an on-demand hot-water heating system or considering a plastic-lined tank or a commercial stainless-steel unit.  If you do switch to an on-demand system or tankless system, it will be necessary to have at least a Corrosion Check of your water completed to make sure that the level of total hardness, alkalinity, and other cations and anions is not excessive.  The KnowYourH2O Team recommends pretreatment of your water if the total harness exceeds 100 mg CaCO₃/L, if the local water company uses a phosphate chemical to sequester metals,  or if the water has an alkalinity, chloride, sulfate, or total dissolved solids that exceeds 200 mg/L. A common pretreatment system for this application is a water softener, we do not recommend a salt-free conditioner for this application. 

Treatment Systems

Crystal Quest- Water Softener
US Water Systems – Matrixx Water Softener

We recommend getting your water tested and sending the testing results to the water professionals to properly size your system. 

Quote: “Hard water treatment is generally recommended by the Water Quality Association and equipment manufacturers when the hardness exceeds 7 grains per gallon (120 mg/l). Based on nearly 15 years of experience selling tankless water heaters, we agree that most installations with hardness of 7 grains per gallon (120 mg/l) or greater will indeed benefit from treatment. Where hardness exceeds 12 grains per gallon (200 mg/l), treatment is strongly recommended.” (Source)

If sediment is entering or leaving the system, you might want to consider a RUSCO 1-1/2-60 Hot Water Spin-Down Filter System or a Spin Down Filter with Autoflush. You would install this on the inlet side of the water-heating tank. 

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