Can I shorten the PVC pipe?

Problems related to residential installations.

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Can I shorten the PVC pipe?

Post by MIKEMCD77 » Thu Dec 21, 2017 3:17 pm

On the roof above my furnace, I think there’s always been a vent (that’s about a foot tall) with a "mushroom" cap. However, about 17 years ago when I had a NEW furnace installed, the installer cut a hole in the mushroom cap and then ran the PVC pipe from the furnace up THRU the mushroom cap... and the PVC pipe extends another foot above the mushroom cap. He then placed a U-joint on top of the PVC pipe (to prevent rain from entering it).

I want to replace the U-joint (or shepherd’s hook) with a “terminator” device. My QUESTION - wouldn't it be OK to saw about one-half of the PVC pipe off? (Again, the PVC pipe is at least a one-foot extension above the "mushroom"... and the mushroom sits on top of a pipe that is at least one-foot long.)

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- Can I shorten the PVC pipe?

Post by Freon » Sun Dec 31, 2017 10:02 am

Not knowing your roof design or prevailing winds that's not an easy question. The manufacturer of the new furnace should have guidelines for the venting of the furnace. Absent those you can try shortening the vent and see how it all works. Just don't use PVC cement until you know all is working. That way you can go back to the original height.

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