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secutanudu 03-02-2011 11:59 AM

Vent pipe - horizontal?
I had a major roof leak this winter due to an ice damn around a vent pipe protruding through the (close to flat) roof.

This vent pipe goes up an outside wall and straight out the roof. I have VERY small eaves, just a few inches, so the vent pipe is probably less than a foot from the edge of the roof. The second floor is a finished attic, so there is no attic space above. Basically it's a finished bathroom, 2x6 ceiling joists with the roof decking right above.

I am thinking of relocating this vent pipe. Can a vent pipe go up the outside wall, turn horizontal once it hits the ceiling of the bathroom. This way I could extend the vent pipe a few feet into the bathroom, then go up out the roof not so close to the edge. I assume the pipe has to be pitched towards the inside of the house, and I'm not sure I have the room to do that properly in a 2x6 cavity.

Is this allowed? Will it compromise the functionality of the vent?


md2lgyk 03-02-2011 05:38 PM

I'm not a professional, just an educated DIYer who built his own house himself. As far as running the vent horizontally, as long as the horizontal portion is above the flood level of all the fixtures in the house, it should work fine. I don't have any idea what code says about running vents on the outside of the house. I see it all the time where I live, but that doesn't mean it's legal.

If your jurisdiction allows them, you might consider an air admittance valve instead of a pipe through the roof (as long is this isn't the main house vent).

I'd suggest calling your local building city/county building department and asking them.

TheEplumber 03-02-2011 06:05 PM

199 Attachment(s)
You can run the vent horizontal, you will need to support it every 4ft and put 1/4" per foot grade on it (graded back to the fixtures) Chances are that you will have to bury the 90 into the top plate- not easy to do with a roof on top

secutanudu 03-02-2011 06:23 PM

It is the main house vent, so an AAV is a no-go. Ugh, this is a new vent, I wish it was done this way when it was put in 6 months ago, I just most of the plumbing done over in my house (remodeled both bathrooms).

The question is, do I patch the hole 4" from the edge of my roof and make ANOTHER hole several feet up....or do I hope the current leak was fixed and not do anything?

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