What causes the loud banging noise in my homes pipes?
The problem you are describing is often called water hammer. It can happen on a normal faucet, but is more common on pipes attached to a washing machine or dishwasher. In both of these machines, the valve is electrically operated — it’s called a solenoid valve (see How Electromagnets Work for a discussion on solenoids). Solenoid valves close very quickly. Imagine the following scene. The washing machine is filling, so the valve is open. Water is rushing through the pipe toward the washing machine. When the washing machine is full, the valve slams shut very abruptly. In the pipe, there may be 5 or 10 pounds of water that had been moving at a significant speed, and now it suddenly comes to a complete halt. The water’s momentum carries the entire pipe system forward, and it’s the shifting of the pipes that makes the noise. If it is a long, stra
