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Eliminate the “water hammer” effect
Aug 26, 2005

When you close a faucet or an appliance shuts off, you may hear a banging noise known as a “water hammer.”   This condition results from water moving under pressure suddenly being stopped by the closing of a faucet or valve — the pressure forces the pipe to shake and may damage the valve. 

If your house is not equipped with water hammer arresters, or air chambers, install one for each affected fixture.  This  air chamber can be made from copper pipe and must extend upward from the water line for a recommended distance.  A copper cap is soldered to the top end of the pipe. The copper pipe should be twice the diameter of the supply pipe.  Air inside the chamber cushions the water pressure and stops the water hammer.

There are several other types of water hammer arresters available. You can also purchase a coil of specially-made flexible copper tubing, which can be installed without cutting into the wall. An almost-round model has a ring around its centre.  

The first two types sometimes fill with water. If that happens, turn off the main water supply and open all the faucets. When they have drained, close the faucets and turn on the main water supply. Inside the ball model is a diaphragm which may tear and the unit will need to be replaced.

A pressure-reducing valve can stop a water hammer by lowering water pressure to the house, but it may reduce water flow, affecting upper-floor fixtures.  The valve can also correct a whistling sound, which may indicate high water pressure. The whistling may also mean that water flow is restricted, so make sure all valves in the supply lines are fully open.

Other plumbing noises

Loose pipes may bang as water is turned off. Check the pipe clamps or hangers and re-secure them or add more fasteners if necessary.  If a pipe bangs as it passes through a stud or sill, enlarge the hole.

A pipe should be able to slide slightly on its hangers. When you turn on the hot water, a cold pipe will expand, and a clinking or ticking sound means the pipe is too tightly anchored. Listen to locate the sound and then search along the pipe to find the tight place. Then, loosen the support and add a piece of rubber or felt between the pipe and support to fix the problem.

Running water sounds may come from an open faucet, a leaking toilet, a furnace humidifier connected to the cold-water line or an automatic water softener when it back-flushes. 

Drainage system noises may be from faulty venting, a plugged vent or incorrect drainpipe size.

For more specific information regarding a particular plumbing problem, contact a certified, registered professional plumber.