Plumbing – Sound of Running Water After Faucet is closed

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In addition to a "whooshing" sound when water is running through our pipes, I've noticed recently that after we turn off a faucet the sound of running water continues for about 5 seconds. What would cause this?
I recently replaced the main shutoff valve since it was leaking. I don't think there is air in the system. All of the faucets and showers have been used extensively since then. Could the whooshing water sound and the delayed shutoff be related? They both started after I replaced the main shutoff.

Best Answer

I've heard this before, in a single story house where the water main entered the building near the bathroom, but because there was a hallway with a solid floor between there and the kitchen, the hot and cold pipes ran up through the attic, then back down to the sink and dishwasher. All was fine for years until some work was done in the bathroom, moving a sink, then the exact same issues started that you describe. What happened was that there was air in the inverted U in the pipes, and even with the kitchen sink on full blast, there wasn't enough flow to push the air through the pipes, so each time the water ran, it would push the air over to the downward leg, then the water would fall through the air and feed the faucet, and once the faucet was shut off, the water would continue to fall through the air until the air was back at the top of the U.

I fixed this temporarily by removing the hose to the dishwasher, the flow was then high enough to force most of the air out, but a more permanent fix was to reposition the pipes so that the air gravitated back to a bleed point I installed.

I'd suggest you look at the pipe routes to see if there is anywhere that the air introduced while replacing the shutoff can be accumulating that it can't easily get out from.

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