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Old 10-17-2011, 03:00 PM
Jinx Jinx is offline
Join Date: Dec 1999
Location: Lost In Space
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Plumbers: Why Do Pipes Screech?

At the office, the Bunn coffee maker with a dedicated, copper water line will start screeching. Then, I found at my in-laws, the kitchen faucet will start screeching - both hot OR cold water. I thought it was the aerator, but I understand their shower will do the same (for only hot water). What causes this? And, can it be stopped to save our eardrums??? I WAG dirt at the aerator or similar flow restricting orifice???

Last edited by Jinx; 10-17-2011 at 03:02 PM.
Old 10-17-2011, 08:37 PM
cornflakes cornflakes is online now
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Location: Bubbaville
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It screeches for the same reason that bagpipes and woodwind instruments screech when played by someone without experience. The water is flowing past a restriction and into a length of pipe that the right length and shape to resonate. I think that changing the restriction (ie, opening or closing a valve.) or damping or changing the length of pipe or tubing should help.
Old 10-17-2011, 10:41 PM
GaryM GaryM is offline
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I've been told, by my Dad who wasn't a plumber, that it could be caused by a loose washer in the faucet. Of course many modern faucets no longer use washers.
Old 10-18-2011, 12:25 AM
GreasyJack GreasyJack is offline
Join Date: Feb 2008
Location: Montana
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If this Bunn brewer is like the kind I used to fix long ago, they are indeed prone to screeching. The way these brewers work is that when you push the brew switch, it opens up the boiler fill valve for a set amount of time, and the boiler overflows into a tube leading to the brew head. This means that in order to get consistent portions, the inlet flow has to be consistent. So there's a flow regulator on the back of the brewer that reduces the incoming torrent to whatever trickle they want to come out of the brew head. If the flow going into the regulator is unusually high, or if the regulator itself is worn out or has some gunk in it, the thing will screech like crazy.

The proper fix is for someone to come out and add in another in-line regulator to step down the flow before it hits the regulator on the brewer, or even just adding a water filter can work. As a temporary fix, you might be able to turn the water shut-off a 1/4 turn or so, although this may just migrate the noise to under the counter and might cause the valve to leak.
Old 10-18-2011, 01:20 PM
Jinx Jinx is offline
Join Date: Dec 1999
Location: Lost In Space
Posts: 7,818
Thanks, all. I am familiar with the bagpipe analogy, and I reasoned there must be a blockage. But, that puzzles me for (a) if it is corrosion building up on the pipe walls, my house should be squealing like a banchee (with fair, well water quality) as opposed to my in-laws with superb, municipal water quality. Also, (b) the noise seems to be at the faucets, but sound can be deceiving. Maybe the faucet is simply acting like the bell of a horn? Last, (c) it is always possible their hot water heater needs a flush. Even the best water has sediment.

As for the Bunn unit, thanks for the detailed explanation. I bet you're right on the money because you can hear some internal reservoir filling while it screams...and then stops while brewing the coffee (with the reservoir now full and well-heated), more or less.


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