Sometimes its the toilet. In a toilet, this is typically the fill valve. When the fill valve diaphragm gasket inside the top cap of the fill valve goes bad, it looses its elasticity. The softness that once allowed it to form around the shut off seat
inside the valve and shut off the water completely, is gone. The gasket becomes hard like a superball. When it tries to shut off, it bounces in micro vibrations sending a shock wave back into the piping. It
vibrates with a similar pattern to tuba players lips. Since the piping is metal, like an instrument, it creates a sound very much like a trumpet. Replace the
fill valve if it is the offending part, (they are relatively inexpensive) and the noise from the toilet will quit.
Another problem is water hammer. This happens when you have high water pressure. Water moving in one direction does not want to stop flowing. When you shut off a faucet, the water still has some force which has to be absorbed. This force is usually absorbed in the piping. It‚Äôs like when you try and
stop a car, you feel the momentum carry you forward. This same momentum occurs in water. When you shut off the faucet, the pipe will flex up trying to absorb the force. If it's near wood, it will bang against the wood. You can stop this by installing water hammer arrestors on the offending water lines.
Some noises are caused by pipes that are improperly strapped or that the strapping situation has changed. The straps have become loose or the holes that were
drilled are too tight. Since pipes are made of metal, they transmit sound throughout their length. As water flows through the system, it flows over obstructions and around turns...when it does this, it creates
eddies in the water. These can be rhythmic depending on the speed of the water. When they reach a certain pitch, they cause the piping to begin vibrating in harmonic reaction to the wave created inside the pipe. In order to stop the noise created, you have to remove the offending part or debris that's causing the water to fluctuate.
Water pipes also expand and contract, this expansion and contraction can rub against the studs and joists inside the walls. When cold water enters a pipe that has acclimated to the ambient temperature of the air inside the walls, it begins to contract and conversely
when hot water enters the pipes that have cooled to the air temperature, they expand. Pipes that are either strapped too tight or not strapped properly will either pop or grind.
You may think the inside of your pipe is completely smooth because it feels that way to our fingers. That is only the fact that we don't have enough nerves in our fingers to actually feel the roughness of the pipe. Under a microscope, the inside of a pipe looks like the rocky bottom of a river. So the water begins to swirl as a layer of water is caught in the resistance of the pipe surface. As the layer next to it begins to travel faster it actually tumbles over
the lower layer. The faster it goes, the larger the swirls become. At 10 feet per second they begin to set up a harmonic vibration in the piping. If the pipes aren't supported properly, you will have rattling and banging.
Check the pressure from the city and if you have a pressure reducing valve you may need to have someone check the pressure of the house to see if its over 80 psi. In addition, a restriction on the inside of the
piping can cause the same effect. Kind of like putting a whole lot of boulders in a small creek, you can hear the creek from a long ways away as it rushes over the rapids. A gasket from a valve will become a flapping vibrator that will send a harmonic noise through the pipes like a saxophone.
A loose rubber washer inside a faucet, valve or check can cause this same problem.
Raymond VinZant Plumbing Prof.