Can I use PVC for Bathroom venting through attic

[Jack]

Need to vent bathroom fans through roof.

Can I use PVC pipe? (I just know how to use PVC, and am horrible with metal ducting.)

[Ken]

Yes, you can use PVC pipe, but you still need to use a roof cap. You can't put the PVC pipe through the roof with a boot like you would with a plumbing vent.

Ken

[Jack]

I redid the roof last year, an I installed a tin flashing with the round rubber seal kind of thing.. in anticipation of bringing the vent up through the roof and through the flashing/rubber seal... Are you saying that is not a good idea?

[Ken]

If I understand you correctly, that is a bad idea. Rain will come in that way. Of course this is OK for a plumbing vent, because all the rainwater will do is run down the drain. If this is for a fan that vents the moist air to the outside, then whatever amount of rainwater that goes down the pipe stuck through the roof will start coming in through your bathroom fan. That's the reason for for a roof cap, to let the moist air out while preventing rain, snow, leaves, etc from coming in through the vent.

Something like this is what you want:

Ken

[SQLit]

Are you in an area that freezes? If so you might want to rethink the plastic idea. But then again vents are stubbed through in plastic. Around here at least.

[Jack]

yes, I am in area that freezes.. what would the problem be.. there would be nothing but air and vapor in the pipes... what am I missing

[CBHVAC]

Run your PVC, its ok to do...when you get to the roof, extend it up, and put a couple of street 90s on it to make a nice 180 facing back down, to keep water out of it.

[mm]

The metal ducts from my bathroom fans go to within 6 inches of the ridge vent, and then terminate, INSIDE the roof. Is that ok? Maryland.

They're not exactly vertical, one leans forward and the other backwards, both towards the ridge line of the house, so they are only about 4 inches apart where they terminate.

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[Andy Hill]

No, it's not OK. It's a fairly common hack job, but you get way more moisture inside the attic than you should. Mold, mildew, rot -- bad mojo all around.

[CBHVAC]

Nope...its not ok. Run them out, and do it the correct way, unlike teh way the original installer did.

[mm]

Thanks to both of you for the help. It will have to wait until spring.

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