Whenever the hot water (but not the cold) is turned on, the pipes make a knocking sound. I read in “The Family Handyman’s” May issue that this is probably a water hammer caused from too much pressure in the line. Do these new water hammer arresters do the trick or would another solution be better? What kind of “fix” am I looking at and at what cost by a professional? Thanks.
Water hammer is not caussed by too much pressure, but rather by high velocity of water flow, coupled with a fast closing faucet or dishwasher (or washing machine valve, but since the cold water also has one this is probably not the case for you), valve. You more likely have a tight pipe in the wall and the sound you hear is it expanding from the hot water and rubbing against a wood stud.