Water hammer sometimes occurs when a faucet is suddenly closed. When
the flow of water is suddenly stopped, its kinetic energy is expended
against the walls of the piping. This causes the piping to vibrate, and
leaks or other damage may result.
Water hammer may be prevented or its severity reduced by installing an
air chamber just ahead of the faucet. The air chamber may be a piece of
air-filled pipe or tubing, about 2 feet long, extending vertically from
the pipe. It must be airtight. Commercial devices designed to prevent
water hammer are also available.
An air chamber requires occasional replenishing of the air to prevent
it from becoming water-logged--that is, full of water instead of air.
A properly operating hydropneumatic tank, such as the type used in
individual water systems, serves as an air chamber, preventing or
reducing water hammer.