What is water hammer, why is it a problem, and what can be done to eliminate it? Last Update: Apr 05, 2005

Water hammer is the instantaneous increase in water pressure that occurs when water flowing in a pipe stops abruptly (as with a snap action valve closing). The resulting pressure shock causes pipes to bang loudly and can result in costly damage to supply pipes and fittings. With small diameter pipes [causing high velocity flow rates] used extensively in residential plumbing system, lack of effective air cushions (water hammer arrestors), and increasing use of rapid shut-off toilet fill valves (plus servo valves in washing machines, etc.), water hammer problems have become more common, troublesome, and difficult to correct.SOLUTION: Toilet fill valves (like the Burlington Brass & Scovill brand ballcocks produced by CESCO) which operate on a pressure differential [i.e. working “against the water pressure” rather than “with the water pressure”], open slightly to relieve pressure increases & shock conditions, serving as quasi pressure relief valves. Since water (unlike air) compresses only slightly at increased pressure, only small amounts of water need to be discharged infrequently, harmlessly, and quietly into the toilet tank.