Another weird thing

I have a 4 inch pvc vent pipe that goes from the basement , through the attic and out the roof. Sticks up about 3 feet. When the wind blows it vibrates or sings. I can hear it vibrate in the bathroom and feel it in the basement. What can be done to stop this? The top is cut off square. Maybe cut it at a 45? or cut a notch in it?
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Van Chocstraw
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I'd try a 30 cut first. Can't hurt anything and it would change the harmonics. You can always buy a coupling and cut that on an angle and slip it over the top to try it. Or just wrap it with some thin sheet metal to see if it helps. You don't want the cut angle to act as an air scoop. I don't know if it would or not, but make the cut on the leeward side anyway.
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wrote:

Vent pipes have a leeward side? <G>
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Just to the extent that it would be the side opposite the local prevailing wind direction. At least, that's my take on it.
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Van Chocstraw wrote:

FOUR inches?
I'd put a cap on it, for no other reason than to keep beavers from climbing down it.
Maybe a series of small holes around the circumference.
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On 1/24/2009 11:49 AM HeyBub spake thus:

Was thinking the same thing, although a piece of screen screwed to the top would probably work as well. Should help to stifle vibrations.

Dunno; that, or cutting it at a different angle, might just make a better "organ pipe" out of it instead of quieting it down.
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4 inches is code in most places. Even if a smaller vent is legal for that part of the system it has to be increased when it goes through the roof. And it can't be covered with a screen as it could collect debris or snow and block the vent.
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What about a old H shaped cowl ? Could be made up from pipe fittings if need be.
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Blue

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Like this http://www.findtheneedle.co.uk/products/450369-h-cowls-chimney.asp in case the H shaped cowl is a UK/Oz only thing.
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A Google search of " 4" vent cowl" and "4" vent caps" reveals a whole range of options that might just be slipped on top.
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ACTUALLY, 3 inch is standard for the vent stack. PLENTY big for quite a large fixture count.
s

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cut it off about a foot above the roof.
s

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Van Chocstraw wrote:

3 feet seems high? I don't know what the height should be but if I remember right most are about 1' or maybe less?
Kevin
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wrote:

Try putting a 4 inch elbow on it. The elbow looks like a trap would look like under your sink, shaped like a U so the wind would have to come in from the bottom, good luck henry
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design, height from roof and any attachments may be code requirements for that area. check with code enforcement officer before alterations........
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