Dear Inspector,

Water hammer (sometimes erroneously called air hammer) is that banging noise you hear in the wall when a faucet is turned off fast. The noise you hear is the pipe(s) banging around and striking the framing or wall. This often occurs with fast closing appliances such as clothes or dish washing machines.

To visualize this phenomenon, turn on your garden hose with a self-closing handle nozzle. Hold your hand on the nozzle handle full spray. Let go real fast. The nozzle shuts off quickly, and the garden hose jumps. This same exact movement is occurring in the wall when you hear pipe or water hammer. The higher the pressure, the more hydraulic energy, the more the noise.

How do your clients repair this condition? If the pipes are accessible, additional securing of the pipes will help. Sometimes lowering the water pressure reduces the noise. One sure way is to have a plumber install air chambers in the water piping near the offending fixture. Air chamber have a captured air bladder inside for the hydraulic energy to release against. Air works well to absorb energy since it is compressible. Water does not since it is not compressible.

Water hammer rarely causes problems in the plumbing system, however, I have heard of it causing failure of poorly executed solder joints. I usually consider it a nuisance condition with repair optional.

Mike Casey
Kaplan Professional Schools
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