A drain piping leak inside of a building cavity can also produce a noise that is hard to track down.
Intermittent noise in attic after outside spigot turned on.
Banging pipes when the water is turned off is an example of water hammer.
In faucets something as simple as a slack washer or untightened screw at the base of the faucet can result in high pitched screeching due to the tremors.
The incoming water will flush the air out of the pipes but not out of the vertical air chamber where the air supply has been restored.
While cold water is running.
It usually occurs at one of these 4 times.
You may also notice sputtering as the air bubble travels.
Alternatively if the water pressure is higher than what the pipes are used to the same shrill sound can occur.
Open your faucets to drain all of the water from your plumbing system.
First turn off the water to the faucet.
Turn off the water supply to your house at the main supply or street level.
Frustrated by the loud knocking noises coming from your pipes.
We had a buzzing sound in the winter that turned out to be the electric meter.
If you re still stumped i would turn off the house s water and check for visible water damage throughout the home and look for water pooling in the yard around the outside of the house or in.
While hot water is running somewhere in the house.
Every winter when it would be 20deg or below the meter would hum.
Install water hammer arrestors.
An outdoor faucet that makes a loud vibrating noise when it s turned on or off probably has a worn out faucet washer.
The sound can occur whether hot water is flowing out of a faucet or going down a drain.
Installing insulation and anchor strapping around the pipe within the wall can usually fix the problem.
It would get louder as more power was being used.
Draining the water system to get water out of the vertical air chambers or installing water hammer arrestors can solve this problem.
After a cold or hot water supply is shut off.
Turn the water back on.
What s most likely causing the problem depends on when you hear the knocking sound.
Both of these issues can occur for several reasons so you may need a professional to evaluate and address the problem.
It happens when water which is incompressible stops suddenly and has no place to go.