DEAR BARRY: We have a 50-gallon water heater in our basement. It's only 7 years old, but it has always leaked from the drain pipe on the pressure relief valve. We've tried everything to stop the leak. We turned down the thermostat, flushed out the tank, and replaced the relief valve twice. But the problem always returns. Why doesn't this leak stop after all we've done to fix it? --Mark

DEAR MARK: Before answering your question, a few words should be said in praise of "temperature pressure relief valves," commonly known as TPR valves. A water heater is not safe without a TPR valve. Its primary purpose is to prevent an explosion when a water heater becomes too hot. TPR valves have been mandatory for all water heating systems since the late 1960s. Before then, an overheated tank could become a bomb, causing massive property damage and possible injury or death to nearby occupants.  more...