Noisy pipes can be caused by several factors. Let’s start with what is commonly known as water hammer. Water rushing through the pipe and out the faucet moves with speed and force. When you shut off the faucet, the water flow is brought to an abrupt halt. But that energy has to go somewhere. So normally in the wall behind each hot and cold faucet is an air chamber in the pipe. It used to be about 10 inches of pipe soldered vertically. Then when the rushing water was stopped it would push up that vertical pipe where it would hit a cushion of air in the pipe. And that would prevent the water force from causing the pipes to rattle, or hammer. Now there are commercial air cushions that are attached to the pipe in the same place and do the same job.
Hammering can develop because over years the air in that little vertical riser is lost, and thus the cushioning effect is lost. You can often correct this by shutting off the main water, opening all faucets and then draining the whole house from the lowest faucet. When you restore water, air will be again pushed into the risers designed to prevent water hammer.
Another cause of plumbing noise is a loose pipe under the house. The flushed water moves rapidly and in large volume and can cause a pipe to sway, setting up a rattling effect. Drain pipes are usually suspended from the floor joists under the house and a little stabilization may be all that is needed. By crawling under the house with a flashlight while someone flushes the toilet, you should be able to find the source by listening and looking.
Whistling or squealing in pipes is often caused by a worn out washer in a faucet or valve. A common source of this squealing is in the valves that connect to the washing machine. If you notice the squealing sound comes when the washer is working, you have an easy solution. First, shut off the valve and check the washers in the hose. Replace if they look worn or cracked. If that isn’t it, shut off the house water and repair the faucet. One of the faucet’s washers is likely worn or the valve seat is worn, causing water to be forced through a smaller opening and setting up the noise.
Another source of squealing, particularly when it seems to resonate through the whole house, can be either the main shut off valve for the house or the water pressure regulator. For the main shut off, turn off the water at the street valve first and then replace or repair the main house valve. If that isn’t it and you have a pressure reducer on your incoming cold water line, it may be in the reducer’s manifold.
Yet another noise problem can come from the toilet. If, after flushing, you hear a banging or rattling at the end of the fill cycle, then it is likely that the ballcock assembly, which controls the fill process, is worn. Depending on the style and how new it is, you might be able to repair it. Otherwise, replace it with a better one.