Water pipes can vibrate and make noises for several reasons, including air hammer, water hammer and pipes that lack adequate support in the plumbing system. Also, a faulty toilet valve sometimes causes vibration in the pipes upon flushing the toilet.
Air hammer is a knocking noise that occurs when occupants turn on a faucet. It is due to air in the water pipes. Correcting this problem requires turning off the water supply and opening the lowest valve in the home. Once all the water drains from the system, the homeowner refills it by leaving the valves open and turning on the water. As water begins to flow without air from each faucet, he closes it.
Water hammer occurs upon shutting off the water valves. Correcting water hammer usually requires installing water arrestors to slow the flow. Stopping vibration due to unsecured pipes requires adding pipe strapping between the floor joists or studs to secure the pipe.
The toilet fill valve has a rubber gasket near the top of the valve that begins to vibrate with wear. These vibrations travel back through the supply line into the pipes in the walls behind the toilet. The fill valves are relatively inexpensive, making replacement the simplest way of remedying the problem.