Speaker 1: Welcome to brain Stuff from how stuffworks dot com where
Speaker 1: smart Happens. Hi. I'm Marshall Brain with today's question, what
Speaker 1: causes the loud banging noise in my homes pipes? The
Speaker 1: problem of pipes banging in the wall is often called
Speaker 1: water hammer. It can happen on a normal faucet, but
Speaker 1: it's more common on pipes attached to a washing machine
Speaker 1: or a dishwasher. In both of these machines, the valve
Speaker 1: is electrically operated. It's called a solenoid valve. Solenoid valves
Speaker 1: close very quickly, so imagine the following scene. The washing
Speaker 1: machine is filling, so the valve is open. Water is
Speaker 1: rushing through the pipe towards the washing machine. When the
Speaker 1: washing machine is full, the valve slam shut very abruptly.
Speaker 1: In the pipe, there may be five or ten pounds
Speaker 1: of water that had been moving at a significant speed,
Speaker 1: and now it suddenly comes to a complete halt. The
Speaker 1: water's momentum carries the entire phipe system forward, and it's
Speaker 1: the shifting of the pipes that makes the noise. If
Speaker 1: it's a long, straight pipe carrying the water, the amount
Speaker 1: of motion and therefore the noise can be especially significant. Obviously,
Speaker 1: this is not good for the pipes. Each time you
Speaker 1: hear the noise that means your pipes have been stressed
Speaker 1: and flexed. The normal solution is to put a shock
Speaker 1: absorber in the pipe near the valve. A simple shock
Speaker 1: absorber would be a foot long piece of vertical pipe
Speaker 1: attached near the valve. This pipe is filled with air.
Speaker 1: Now when the valve closes, the moving water rushes up
Speaker 1: into the vertical pipe and compresses the air so it
Speaker 1: slows down gradually. The problem with a simple vertical pipe
Speaker 1: is that the bubble can get dissolved into the water,
Speaker 1: so a sealed system using a rubber bladder can be purchased.
Speaker 1: This solution also allows you to orient it other than vertically.
Speaker 1: Another approach is to use a spiral of copper pipe.
Speaker 1: When the water hits the spiral, the coil absorbs the
Speaker 1: shock like a spring. Do you have any ideas or
Speaker 1: suggestions for this podcast? If so, please send me an
Speaker 1: email at podcast at how stuff works dot com. For
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