Why does my hot water smell?

Why does my hot water smell?

Most of the time the rotten egg smell you experience from the hot water faucet is cause by hydrogen sulfide gas.  Three ingredients are required to generate hydrogen sulfide odor that gives water its rotten egg smell: sulfur, hydrogen, and bacteria.

If any of the above elements are removed there should be no odor. It is not always possible to remove the trace of sulfur that is present in most water, and corroding metals generate hydrogen. Sulfur eating bacteria are resistant to heat up to approximately 225ºF. They are both water borne and air borne.
Potable water is seldomly pure H20.  It is a mixture of water, oxygen, calcium, magnesium, fluoride and other particles.  The content of potable water will vary from one geographic location to another.  The above ingredients add such things to the water as taste, color, odor and the ability for the water to be conductive (electrolytic).  Conductivity allows for electricity to flow through the water resulting from the movement of electrons from one metal (anode) to another metal (cathode.)  This is similar to a battery where the anode is the negative terminal and the cathode is the positive terminal.  The amount of electricity can be controlled by varying the water chemistry (electrolyte) or changing the metals used in the reaction.
Water heater tanks are typically constructed of steel with a porcelain enamel (glass) lining.  A perfect glass lined tank, without an anode rod, would generate such a small quantity of hydrogen that it would not create an odor.    However, due to production and assembly methods it is not always possible to obtain complete coverage of the steel tank.  Therefore, it’s necessary to provide a different metal (anode) to inhibit corrosion of the tank (cathode).
What is an Anode rod and what does it do?
The anode supplies electrons to the cathode and releases positive hydrogen ions and positive metal ions to the water.  Release of the positive ions make the anode appear to dissolve which is a planned and expected situation.  Consequently, the anode is frequently referred to as a “sacrificial rod.”  Electrons travel to the cathode and combine with the hydrogen positive ions to eventually form H2 gas.  No metal is lost at the cathode as it is protected by the anode.  Due to generation of hydrogen ions at the anode, it is possible for hydrogen gas to form which is explosive and warnings are placed on every unit, including the installation instructions, to alert homeowners about the danger of flames near the water outlet.

Water heater manufacturers attempt to produce a standard product that will satisfy the majority of customers. A magnesium anode will satisfy the majority of water chemistry situations.  Extremely hard water or high conductivity areas may require an aluminum anode evidenced by a high turnover rate of water heaters, coffee makers and other using appliances.

Hydrogen sulfide odor is due to the presence of sulfur, bacteria and hydrogen ions in the water.  Refer to the separate Field Service Bulletin “Hydrogen Sulfide Odor.”  Complete removal of the anode, magnesium or aluminum, will void the warranty and shorten tank life.
The magnesium anode installed in the tank protects the tank surface but generates enough hydrogen to create an odor problem when the hydrogen reacts with sulfur and bacteria. Removal of the magnesium anode and replacement with an aluminum anode may minimize the problem. Complete removal of the anode (magnesium or aluminum) will void the warranty and shorten tank life. The only satisfactory method to control the hydrogen sulfide odor is to control the bacteria. As a rule, public water supplies that are properly chlorinated will kill the bacteria. A private well system may be contaminated but, as a rule, it is the pneumatic tank and piping that is contaminated. A contaminated system can be decontaminated by use of a chlorine injector or other purification systems such as ultraviolet. This will destroy the bacteria.

The following steps outline the proper procedure for chlorinating a water heater:

  1. Turn off the water and power supply or gas supply to the water heater.
  2. Drain several gallons of water from the drain valve on the water heater.
  3. Remove the Magnesium anode rod.
  4. Pour a ½ to 1 gallon of bleach into the water heater through the hot water outlet opening.
  5. Install the Aluminum anode rod. (To purchase an Aluminum Anode rod click here)
  6. Re-connect the hot water supply line to the hot water outlet on the water heater.
  7. Turn on water supply and draw water at each hot water faucet in the residence until a Chlorine odor is noticed.
  8. Once the Chlorine odor is noticed turn off the faucets and allow the bleach to sit in the water heater and water lines for a minimum of 3 hours, but a full day is desired.
  9. After Step 8 has been satisfied turn on and draw water at each hot water faucet in the residence until a Chlorine odor is no longer present.
  10. Turn on the power, or gas supply to the water heater.
Once all of these steps have been followed the water heater can be restored to its normal operating function. If you need to chlorinate your well system or other water system(s) consult your plumbing professional or the supplier of that water system. If you have any additional questions you can call our Technical Support Personnel at (269) 683-8549
To Purchase an Aluminum Anode Rod
Click Here
Where is the “anode rod” ?
For most water heaters, the anode rod is attached to the hot water outlet of the water heater. If you are facing the front of the water heater (where the labels are), the hot water outlet is on the left hand side. Other water heaters may have a separate plug beneath which the anode rod is attached.  The anode rod is often referred to as a “sacrificial rod”.