Strange banging sounds in the night? Water hammer is a series of pressure shocks created by a sudden change in flow velocity of a liquid in a pipe. It is a hazardous condition that should be eliminated from any fluid system.
Design a system that minimizes the possibility of water hammer. Holding flow velocities to about 5 fps (based on water) should eliminate hammer. This flow level requires large piping.
Locate any undersized pipe and replace it with a larger pipe.
Secure loose pipes to a wall with pipe clamps to try to remedy the problem.
Wrap some insulation (a towel, an old shirt) around the pipes that are rattling. Sometimes that's hard, because the pipes might be located behind a wall or ceiling where you can't reach them.
Consider that, if your plumbing system includes air chambers, the chambers may have filled with water. To correct this problem, turn your water off at the main shutoff valve, open all your indoor and outdoor faucets, and let the water drain out. When you open the main valve, the water will bypass the air chambers, leaving them full of air.
Think about installing an air chamber (one or more) if your plumbing system does not include one.
Install a water hammer eliminator if securing the pipes does not solve the problem. This device works like an air chamber or shock absorber and is added in-line to the plumbing system.
Increase the time of change in places where there is a sudden change in fluid velocity. For example, quarter-turn ball valves are a common source of water hammer. A slower-acting globe or gate valve will prevent water hammer.
Increase the time for valve change with motorized or pneumatically activated valves. In the case of pneumatic valves, adding a restriction to the exhaust vent can often produce the desired effect.
Use a stand pipe upstream of every valve. You can quickly and inexpensively construct a stand pipe from a capped length of pipe or tubing coming vertically off the main line.
Add an accumulator or desurger if the hammer comes from suddenly starting or stopping a pump. An accumulator consists of a simple tanklike reservoir near the pump discharge. Desurgers incorporate a gas-loaded internal bladder and orifice for harsher shocks.
Slow-acting valves, accumulators, desurgers and variable-speed pumps that start slowly and bypass loops in appropriate zones are also good. Water hammer can also occur in gravity pipes. There are several main causes: pump starting and stopping, closing of valves, fire and sluicing hydrants, the presence of air or the incorrect use of protective equipment.