Q: I have a very bad hydrogen sulfide smell in my private water system. We bought this house a little more than two years ago and I put a new water heater in at that time. According to the home store where we bought the heater, it doesn't have the magnesium anode rod. My question is, why couldn't I add chlorine to the tank? Wouldn't I just need a formula for quantity and how frequently to add it?--J.B.
A: I have received several letters and e-mails concerning odors in water systems. And I've experienced the problem firsthand while inspecting a home recently. The following are excerpts from a news bulletin supplied by State Industries, a leading manufacturer of water heaters in Ashland, Tenn.:
"There are many misconceptions regarding the development and treatment of smelly water in water heaters. The most common odor complaint (rotten-egg smell) is derived from hydrogen sulfide gas dissolved in the water. Concentrations of as little as 1 ppm (parts per million) can result in this odor. The smell is the result of four factors, which must all be present for the odor to develop in a water heater:
- "There must be a high concentration of sulfate in the raw water (typical of well water).
- "There must be little or no dissolved oxygen in the water (also typical of well water).
- "There must be sulfate-reducing bacteria within the water heater. This bacteria is nontoxic to humans and originates in the water source.
- "There must be an excess of active hydrogen in the tank. This may be provided by the cathodic action of some anode rods in glass-lined water heaters.
"With these factors present, the hydrogen and sulfur combine to form the hydrogen sulfide gas that gives off the (rotten-egg) odor to the water. Active use of the water heater will reduce the problem, but idle water heaters (such as during vacations) will allow the accumulation of this hydrogen sulfide gas and aggravate the odor problem.
"Smelly water can most easily be eliminated or reduced by chlorination of the hot water system (both the water heater and all hot water lines) to kill the sulfur-reducing bacteria and replacement of a glass-lined water heater's anode rod with one of a less active material.
"Note: Only glass-lined water heaters are equipped with anodes; therefore, chlorination of the system may be the only treatment necessary for some water heaters. In most cases, replacement of the glass-lined water heater's anode with one made of a less active material and chlorination of the hot water system will reduce the production of hydrogen sulfide gas to an acceptable level.
"After removing the existing anode rod, household bleach must be added to the water heater tank at a ratio of one cup for every five gallons of water heater capacity. Bleach may be poured directly into the anode opening or through any other water fitting on top of the tank.
"Install the new, less-active anode rod and refill the tank completely. Turn on each hot water tap slowly and allow the water to flow until the chlorine can be detected. Turn off the hot water taps and let the water stand in the hot water distribution piping for no less than two hours (preferably six to eight hours or overnight). Flush the complete hot water distribution system through each hot water tap after the chlorination treatment."
(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at PO Box 268, Evansville, IN 47702 or send him e-mail at d.barnett@insightbb.com.)
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