Frozen Vent Pipe


Old 01-08-04, 01:22 PM
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Unhappy Frozen Vent Pipe

Okay, I can't remember if I've asked this before or not, but, since it has been very cold up here in the Bush, I'll ask anyways.

This past week it has been cold, -30C, and as usual the sewer vent pipe has froze up. This means the husband has to go up on the roof top and defrost. Just a little bit of a safety concern going up the 6/12 pitch roof with ice and snow and such.

So, I've heard about a "frost free vent" that is used in Minnesota, however, everyone I ask, including contractors in my area have never heard of any such thing.

So, does anyone have any ideas how I can prevent this from re-ocurring?

The stack extends past the peak of the roof and is about two feet from the peak. I don't know if this info is needed, but what the heck.

Anyways, any suggestions would be greatly appreciated.

Ciao, from the frozen north!!
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Old 01-08-04, 01:29 PM
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What is done on venting in cold climates is the vent is sized larger just below the roof inside the attic. Usually one pipe size larger, but i've seen 2 sizes larger.
The thought process behind this is it will take a much longer time for the hoar frost from condensation to bridge the larger opening and blocking the vent.

That's the general idea....

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Old 01-08-04, 01:31 PM
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Never heard of a "frost free vent", but then again I'm from the sunny South, where some years we don't even get enough snow for it to even stick.
I would think that you could put a cap or double 90s to create a downlooking U to prevent ice and snow from getting down into the vent and freezing up.
Check with your Building Inspection Department to see what they allow.
Good Luck!
Edit: notuboo posted while I was typing. Didn't know that frost from condensation could block a vent. If that's what it is, then obviously capping it would make it worse. I learn something new every day.
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