| A Rotten Egg Smell in the Washer |
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By Dwight Barnett
Scripps Howard News Service Question: We have a vexing conundrum in our utility room. We are served by the municipal water department. As a rule, the water is odor-free. The utility room is served through a separate feeder line. We have a 15-gallon electric water heater for the washing machine. When my wife fills the washer with hot water, however, there is a distinct odor, which I believe to be hydrogen sulfide. The odor is noticeable only when hot water is used. Any suggestions you have as to the possible correction would be greatly appreciated.-- J.P.H., Tell City, Indiana Answer: You're right about the hydrogen sulfide odor being from the hot water supply only. The following information was gleaned from the "Fundamentals of Water Heating Training Manual" from Rheem Manufacturing Co.: "Hydrogen sulfide is a gas that is present in some water systems. The amount depends on where the water comes from, though virtually all water in the United States comes from ground water or surface water sources." We need to see how much of the water we use passes through the heater, because as the water is heated, the dissolved gases are released. If the water contains as little as one part per million of hydrogen sulfide, you will notice its distinctive rotten egg smell. The odor is most noticeable when the heater is first used. The odor can also be caused by the anode rod inside the heater. The anode is a sacrificial metal rod that attracts corrosive elements in the water supply to protect the lining of the tank. Most anode rods are magnesium. In water supplies that have "low conductivity," the anode rod operates at low current levels, releasing a small amount of elements from the rod to the water. When the conductivity is high, an excessive amount of inefficient current is produced, releasing larger amounts of elements to the water. When excessive elements are freed to the water, chemical reactions take place, producing hydrogen ions. Some water supplies have excessive sulfates along with strains of sulfate-reducing bacteria. The bacteria are harmless, but under certain conditions they can grow and produce hydrogen sulfide gas by using the hydrogen ion released from the anode. Sulfide-reducing bacteria in the water heater can be killed by adding chlorine to the tank. This should be performed by a licensed plumber. The anode rod can be replaced with a substitute metal rod. Water samples should be analyzed by a qualified laboratory to determine the type of anode best suited for your water supply. Because sulfate-reducing bacteria cannot grow in the presence of atmospheric oxygen, the rotten egg odor will not be noticeable at cold-water outlets. (C. Dwight Barnett is a master inspector certified by the American Society of Home Inspectors. Questions may be addressed to him at P.O. Box 14091, Evansville, IN 47728, or e-mail him at barnett@evansville.net.)
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