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Q.I have an A.O. Smith water heater with a faulty polypropylene dip tube. Your report on dip-tube failures ( Notebook, 7/99) said that a faulty dip tube may need to be replaced with a new copper dip tube. However, the tech support people at A.O. Smith told me that using a copper dip tube will destroy my water heater, and is not recommended. What’s the story?

A.Master plumber Rex Cauldwell responds: The report was mistaken in advising that defective polypropylene dip tubes should be replaced with copper dip tubes.

For those of us old enough to remember, dip tubes were originally made of glass. Since they had a habit of breaking during transit, the transition to plastic was inevitable. And perhaps it was just as inevitable that they would keep making them cheaper until they failed. Most plastic dip tubes have not had any problems. The only dip tubes with reported failures are polypropylene dip tubes manufactured by Perfection Corporation between August 1993 and October 1996. More information on the failures and the class-action settlement can be found at www.diptubesettlement.com.

Failed dip tubes are repaired by either replacing the water heater ( usually at your expense) or by installing a new plastic dip tube (usually at the manufacturer’s expense). Copper dip tubes should not be used, for several reasons. A copper dip tube would void the warranty of the water heater. Corrosive water can attack a copper dip tube. Finally, since copper is more "noble" than a water heater’s anode rod, the anode rod will die an early death, and so will the steel water tank, as the tank tries to give itself up to save the copper.