WEBVTT - What causes the banging noise in my home's pipes?

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<v Speaker 1>Welcome to brain Stuff from how stuffworks dot com where

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<v Speaker 1>smart Happens. Hi. I'm Marshall Brain with today's question, what

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<v Speaker 1>causes the loud banging noise in my homes pipes? The

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<v Speaker 1>problem of pipes banging in the wall is often called

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<v Speaker 1>water hammer. It can happen on a normal faucet, but

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<v Speaker 1>it's more common on pipes attached to a washing machine

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<v Speaker 1>or a dishwasher. In both of these machines, the valve

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<v Speaker 1>is electrically operated. It's called a solenoid valve. Solenoid valves

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<v Speaker 1>close very quickly, so imagine the following scene. The washing

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<v Speaker 1>machine is filling, so the valve is open. Water is

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<v Speaker 1>rushing through the pipe towards the washing machine. When the

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<v Speaker 1>washing machine is full, the valve slam shut very abruptly.

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<v Speaker 1>In the pipe, there may be five or ten pounds

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<v Speaker 1>of water that had been moving at a significant speed,

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<v Speaker 1>and now it suddenly comes to a complete halt. The

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<v Speaker 1>water's momentum carries the entire phipe system forward, and it's

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<v Speaker 1>the shifting of the pipes that makes the noise. If

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<v Speaker 1>it's a long, straight pipe carrying the water, the amount

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<v Speaker 1>of motion and therefore the noise can be especially significant. Obviously,

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<v Speaker 1>this is not good for the pipes. Each time you

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<v Speaker 1>hear the noise that means your pipes have been stressed

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<v Speaker 1>and flexed. The normal solution is to put a shock

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<v Speaker 1>absorber in the pipe near the valve. A simple shock

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<v Speaker 1>absorber would be a foot long piece of vertical pipe

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<v Speaker 1>attached near the valve. This pipe is filled with air.

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<v Speaker 1>Now when the valve closes, the moving water rushes up

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<v Speaker 1>into the vertical pipe and compresses the air so it

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<v Speaker 1>slows down gradually. The problem with a simple vertical pipe

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<v Speaker 1>is that the bubble can get dissolved into the water,

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<v Speaker 1>so a sealed system using a rubber bladder can be purchased.

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<v Speaker 1>This solution also allows you to orient it other than vertically.

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<v Speaker 1>Another approach is to use a spiral of copper pipe.

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<v Speaker 1>When the water hits the spiral, the coil absorbs the

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<v Speaker 1>shock like a spring. Do you have any ideas or

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<v Speaker 1>suggestions for this podcast? If so, please send me an

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<v Speaker 1>email at podcast at how stuff works dot com. For

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<v Speaker 1>more on this and thousands of other topics, go to

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<v Speaker 1>how stuff works dot com.