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Smelly Water In Water Heaters

How to eliminate water heater odors

Sulfur or “rotten-egg” odors can develop in water heaters and in corroded iron piping even if the water is chlorinated city water. This usually occurs if the water has a low chlorine residual, high levels of sulfates, and/or the water has sat inactive for days or weeks.

Odors are often caused by bacteria. 

The incidence of rotten egg odor or black water in water lines is due to the reaction of sulfates and microorganisms in water. You can determine the source of the odor. It is important to check to see whether the cold water contains odor or just the hot water.

Run the hot water to notice the odor. Then move to another faucet and run the cold water. If the cold water has an odor, then the source is in the cold water, piping in the home or the water system. If the hot water alone has an odor, then the odor is occurring primarily in the water heater. which can be caused by using water during regeneration, depending on the water system you have.

Coldwater Is still having an issue.

  1. check the outside hose bib – The arrow is pointed to a hose bib attached to the home. This hose bib is after the water system. Check the water from here first to determine if it has an odor.
  2. a if it does have an odor, its most likely the water system, or it could be the piping.
  3. b if it doesn’t have an odor then the water system is working and your smell is coming from your pipes or your faucet screens
  4. remove all faucet screens in your home. Clean all screens they could be causing a smell all by themselves.  

Solutions for hot water heater odor

1. Remove the anode rod and sanitize the water heater and hot water lines. They say it will void the warranty on your water heater and corrode the water heater faster. This is correct. Just like the zinc on a boat being the self-sacrificial to corrode first before the boat motor. The fact of the matter is then when you go to return the water heater they never go and check the anode rod. Its either this option or live with the smelly water


3. Odors can develop even in cold water piping in the home, especially in galvanized iron piping. Often iron piping in the house is of an older age and can be corroded and providing a good environment for the bacteria to grow and odors to develop. If there is an odor in the cold water, and the source is chlorinated city water, its best to trace and see if the piping is iron piping, and then replace it with copper. As the first step to this process, one can add hydrogen peroxide or chlorine bleach to the piping and sanitize it, and see if the odor can be eliminated. If the odor returns, have to re-evaluate the situation

Water Heater Odors

Most odors reported on city water, are from smelly water heaters. If your hot water has a sulfur or ‘rotten egg’ odor to it, the odor is being produced right in the water heater.

Almost all water heaters have “anode rods” which in a cathode-anode reaction, produce excess ions that wear off the anode rod and adhere to the inside glass lining of the water heater, preventing corrosion. The greater the activity of the anode, the greater the amount of hydrogen ion and hydrogen sulfide gas. If the cold water does not contain odors, but the hot water does, then a thorough sanitizing of the water heater tank with 1 to 2 pints of store-bought hydrogen peroxide will eliminate the odor.

See the procedure below. If you are not familiar with the functions of your water heater, DO NOT ATTEMPT this yourself. You can have this done by a licensed plumber to avoid damage to your water heater, or causing electrical problems, or gas explosions by improperly restarting the water heater if gas. We offer this information as informational and educational all, and no warranty or guarantees are expressed or implied. If the water heater is old and corroded, cleaning the sediment from the water and sanitizing by chlorination could cause the water heater to leak.

Procedure for Sanitizing of Hot Water Heaters to Eliminate Odors

1. Turn off the manual switch if the water heater is electric. For gas heaters, turn the control to Pilot. Make sure the pilot is still lit so you can restart the water heater when the procedure is completed.

2. Close the cold water inlet valve at the water heater.

3. Open a nearby hot water faucet inside the home and the T&P (temperature and pressure valve, located on the top of the water heater) valve to relieve tank pressure. Note of caution: T&P valves may need replacing if defective or old once you touch them.

4. Drain the water of enough water to compensate for the hydrogen peroxide to be added. Use a hose connected to the drain valve if an open drain is not adjacent to the water heater. Tip: have on hand a hose bib cap, available at any hardware store. When the procedure is completed, in some cases the drain valve will leak, and a hose bib cap can be screwed on the end of the drain valve, preventing the need for a drain valve replacement. Or replace the valve if desired with a new drain valve.

5. Remove T&P valve, anode rod, or disconnect the hot water outlet pipe from the water heater

6. For best results and to preserve the life of your water heater, inspect the anode rod. If corroded, replace with a new aluminum/zinc anode rod, which will create fewer odors. Figure 3 Typical gas water heater cut-away showing anode rod and cold water dip tube.

7. Add 1 to 2 pints of 3% hydrogen peroxide (the kind typically found at drugstores) for every 40 gallons of water heater tank capacity. This can be done by pouring the peroxide into the water heater’s outlet pipe opening or into the T&P valve opening. Re-pipe the water heater and close the T&P. We like to pour the peroxide into the anode rod hole after you already removed it..

8. Open the cold-water inlet at the heater and turn on all hot water faucets inside the house. Shut off all the hot water faucets and let the water sit in the pipes for a few hrs.

9. After a few hours, open all the cold water lines for 5 min on cold only. Then open all the cold water faucets on the inside of the house. Wait to you get peroxide chemicals to every faucet then shut off the water and sit for an hr or so. Be careful because hot water will spit and sputter. This is good it’s getting all the air out of the lines. Do not turn the water heater back on until you get all the air out of the lines.

10. After 15 minutes, purge the hot water supply lines and drain the water from the tank through the heater drain valve, flushing out any sediment if present. Close the drain valve.

11. Make sure you purge all air from hot water lines from the open hot water faucets. Close the hot water faucet after all the air is out of the system.

12. Check for water leaks at all fittings used; repair as necessary.

13. Turn on the manual electrical switch, or turn the gas control knob back to “On” and verify that the heater burners have lit and turned back on.

14. Check for normal water heater operation.

If the Odor Returns to the Hot Water

After this procedure is completed, the odor will be eliminated in almost all cases. However, if it returns within a few weeks, then the sanitizing procedure can be repeated. However, in many cases, the cold water will still have problems with recurring odors due to the continued presence of sulfate bacteria and low chlorine residuals in the water.

Other options for smelly sulfur odors in water heaters are:

1. Remove the standard magnesium anode rod and replace it with an aluminum or zinc anode rod or and odor preventing electrical anode rod. if you haven’t already

2. Replace the water heater with a plastic-lined water heater, or an instantaneous water heater, or a commercial stainless steel water heater (none of which have anode rods). We use a lifetime warranty rheem plastic water heater. Call for details.


Published: November 19, 2019
Author: Crystal Clear Water
Categories : Uncategorized