DWV Vent Question/testing - Plumbing - DIY Home Improvement | DIYChatroom

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Old 12-19-2015, 08:56 AM   #1
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DWV vent question/testing

I was reading a UPC code book (though, not one specific to Massachusetts), and it states that the maximum run for a 2" vent is 120ft, but it can't be more than 30 foot horizontal? Do we need to add bends in the calculation? Or do they not apply here? And how essential is that 30ft rule?

I picked up a future vent in the basement: it runs about 25ft to the fixtures, but there are a couple of 45's and a 90 to make it work.

Then the vent rises 20ft to the attic, but it then travels another 25 feet horizontally to tie into the main stack.

I think it'll pass inspection, but I don't want to be worried about compromised traps simply because I went too horizontal...

Is there a way to test a vent prior to dry walling?
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Old 12-19-2015, 10:56 AM   #2
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Not more than 1/3 of it's length can be horizontal. That equals 40ft, not 30ft
No deduction for fittings
If you increase one pipe size it's entire length- you can then go unlimited distance.

As it is now, you have 50 ft horizontal- assuming a 2" is required, it's up to your inspector to approve or not.
For testing, cap both ends and fill with 5psi of air, Attach to the vent stack after inspection
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