Some homeowners hear a banging, knocking or a clanging noise when they run the water in their house, especially when they shut the water off. Sometimes the pipes sound like they are going to break through the wall when the faucet is turned off. Don't worry your pipes are not possessed and you will not require an exorcism in the house. You have excess pressure built up in your water pipes, more commonly known as a water hammer. Water-hammer is caused by high water-pressure.
Too much pressure in the pipes can cause damage to the plumbing, making repairs necessary. Excess pressure can cause pipe joints to split or crack and relief valves to leak. Thankfully, a quick fix works to quiet you loud plumbing system and saves you the expense of calling a plumber.
Find the shut-off valve for the house. The main valve is usually located in the basement or utility room near the water meter. The main shut off valve is typically a gate valve, which is not a very pretty turn off, it's just a round handle.
Go around the house and shut off all the water valves to appliances including washing machines, hot water heaters, dishwashers, refrigerators and any other appliance that has a water supply.
Turn off the supply valves for the toilet, usually found behind the toilet.
Move to the sink closest to the main supply valve. Open the cold water side and let the water run.
Find the sink farthest from the main valve and turn on the cold water. Leave the cold water open and running.
When it stops flowing from the faucets, turn off the faucets.
Go back to the main water-supply valve. Turn the main supply valve back on.
Open the supply valves for the refrigerator, washing machine, hot water-heater, dishwasher and any other water-supplied appliances.
Flush the toilets beginning with the one farthest from the shut-off valve and working toward the toilet closest to the main supply valve.
Open every faucet in every sink, shower and bathtub. Put on both the hot and cold sides. Don't forget any utility sink that you may have in a garage, basement or laundry room.
Let the water-flow for five to 10 minutes. There will be air in the lines, which causes the water to spit and sputter out of the faucets, this is normal. It can be a little scray and shocking because you don't expect your faucet to spit and hiss at you, but it is perfectly normal. If after 10 minutes, air is still spitting-water out of the faucets, let the water keep running until it flows smoothly. The water may begin to flow smoothly and then suddenly spit and sputter and then flow smoothly again -- normal. Don't turn off the faucets until it runs freely without spitting for at least two to three minutes.
Ahhh Quiet Pipes
That's it! You are all done. After you run through the entire process, your pipes will no longer knock, bang, clang or make other noises when you turn off faucets. If the pressure builds again and your pipes start to make noise, run through the steps to quiet them.
As soon as you hear the signs of a water hammer, discharge the air from the pipes, which is what you just did, to keep the plumbing flowing and avoid an expensive visit from a plumber.