Robert Pelikan takes a closer look at the causes of water hammer and considers some remedies.
We've all experienced water hammer at home -- the shower valve is closed abruptly, or the sprinkler system valve closes at the end of the cycle, or the clothes washer fill cycle ends -- and bam! All the pipes in the house rattle. Any time you have a high flow velocity, particularly in a long pipe run, and there is a sudden change in velocity, water hammer can occur.
The resulting pressure wave is transmitted throughout the system, subjecting every component in the system to pressures approaching 10 times the normal system pressure. The pressure returns to normal only when it is dissipated by friction loss, pipe expansion, or when something gives -- a valve or section of pipe. Let's take a closer look at the causes of water hammer and consider some remedies.