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Old 11-26-2011, 12:12 PM   #1
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Fixture vent sizing

I have a 1.5" pvc pipe that vents my dishwasher and kitchen sink that has to be rerouted. Due to size restrains, using a 1" pipe for the last 3 feet before it penetrates the roof would make my life much easier. Code issues? I want to do this right, not just easy. Thanks


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Old 11-26-2011, 01:44 PM   #2
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According to the regs in my area (which typically follows national standards), 1.5" is the minimum for any vent.


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Old 11-26-2011, 01:52 PM   #3
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Kitchen sink requires 1.5" vent and you can not decrease a vent pipe size.
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Old 11-26-2011, 03:20 PM   #4
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Thats kinda what i thought, thanks for responding
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Old 11-26-2011, 04:12 PM   #5
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you can't reduce vent stay at 1.5 all the way..
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Old 11-28-2011, 08:00 AM   #6
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If legal where you live, just forget the vent line and install an air admittance valve in the sink cabinet instead. That's what I did when I built my house.
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Old 03-18-2012, 11:04 PM   #7
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similar situation for me

Thought AAV's were not code in most places for dishwashers, due to the possible high flow rates. (however this seems bogus to me, with a 1 to 1 1/4" sink drain, a full (8-10" deep min 14x12") sink of water causes massive suction during drainage. How this can be less flow than a 3/4 drainline from a DW is beyond me. Maybe there's another reason?)


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