The general types of noises from pipes found in the home are banging, water hammer, squeaking, chattering and whistling. If there is the sudden appearance of one of these sounds, this indicates that something has changed or failed. Frequently this is the pressure in your house. While this alone will not cause noise, a change in pressure from 60 to 120 psi will frequently make the noise loud enough to be audible and annoying. An immediate suspect should be your pressure reducing valve (PRV).
Banging usually occurs when you turn on your water. This is an indication that your pipes are not sufficiently strapped.
Water hammer is the thump that occurs when you turn off the water at a faucet or an appliance quickly. It is a pressure shock wave caused by a sudden in the plumbing system. Pumps, valves, faucets, toilets and fast-acting solenoid valves are examples of devices that can induce water hammer. This shock wave can exert tremendous instantaneous pressures, sometimes reaching 150 to over 1000 psi. The noise is only an audible symptom of what is going on in the piping. The piping is being subjected to the wear and tear of a multitude of shock waves. The result will be leaks in piping, tanks or fixtures unless the condition is corrected.
Sometimes water hammer is due not to the plumbing in the house in which it is heard but to a condition outside of the house (such as a sprinkler system), or in a neighboring house. In such cases, skillful detective work by an experienced plumber is necessary to ferret out the source of the trouble and to plan corrective methods. Water hammer should not be permitted to go on indefinitely. It can usually be eliminated by the installation of special devices known as shock arrestors on the main line near the meter or as close as possible to the cause of the noise.
Squeaking is caused by the hot water pipes. As hot water moves through the pipes the pipes heat and expand, then when the hot water stops, the pipes cool and contract. This expansion and contractions causes movement against the pipe strapping, which can cause squeaking. Sometimes it can actually sound like dripping water.
Chattering in the piping may be caused by loose pipes, by pipes rubbing against a metal projection, by worn faucet washers or looseness of other inside parts.
Whistling is caused by the speed of water flowing through piping which is usually too small. A pressure reducing valve will help as will a general straightening out of the plumbing system. Whistling is most common at bends and tees in the pipe.