Weil-McLain C-1013 Troubleshooting Manual page 12

The hot water smells like "rotten eggs" (Non-Warranty)
The most common cause of water to smell like "rotten eggs" is a non-toxic
sulfate reducing bacteria. The bacteria usually enters into the water system
through a break in the supply piping or during construction/maintenance of the
supply piping. The bacteria survives in the water system by converting sulfate
(SO4) in the water to hydrogen sulfide (H2S) gas. It is this gas that creates the
"rotten egg" smell. The presence of hydrogen sulfide can also affect the taste of
the water as well. Along with the stench caused by this bacteria, black deposits
(which typically indicate pipe and/or fitting corrosion) may also appear in the
water.
WARNING!
In extremely high concentrations, hydrogen sulfide gas can be toxic.
However, the gas is detectable prior to reaching harmful levels.
The bacteria will thrive in any water system under the following conditions:
• High levels of sulfur in the water
• Activated hydrogen in the water from cathodic reactions within the tank
• Water with little or no dissolved oxygen
• Storing the domestic water below 140ºF
Other causes of smelly water:
• Chlorides of magnesium and calcium gives water a bitter taste
• Chloride of sodium will produce a salty tasting water
• Sulfates above 50 ppm in the water gives the water a medicinal taste
• Carbon dioxide in water with a low pH results in water that is fizzy
• Iron and tannic waters will produce water with a bad taste and odor
Action Item:
- The treatment of this situation requires the water system to be shockchlorinated.
Depending on the severity of the bacteria within the water system, several treatments may
be needed.
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