Why Your Pipes BANG When You Shut Off the Water 🔨

Sometimes you shut off a tap and the pipes slam like someone hit them with a hammer.

What is actually banging in there, when all you did was gently turn off the water?

Water filling your pipes is heavy, moving fast, and unlike air, it barely compresses. Close a valve quickly, and that speeding column of water suddenly has nowhere to go. It slams to a stop in an instant. All that momentum becomes a spike of pressure that hits the closed valve and bounces back up the pipe as a shockwave. The pipe jolts against the framing around it, and you hear a bang. The faster the valve shuts, the harder the slam. This is water hammer.

It isn't just noise. Each shock stresses your joints and pipes, and over time it can crack them. That's why plumbers add air chambers, pockets of trapped air that squash like a cushion to soften the blow.

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