Stack vent size


  #1  
Old 07-07-18, 05:14 AM
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Stack vent size

Sorry for all of my posts, but I need to get the entire plumbing built and ready for inspection as soon as I can.
Can I install a 3" stack up past the wc wye, reduce it to 2" to tie in the kitchen/ shower/ lav drain up to the attic, then open it up to 3" to go thru the roof (to prevent freezing in Maine)? or just run 3" all the way?
 
  #2  
Old 07-08-18, 06:26 PM
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As long as this isn't the main stack, you can reduce it to 2" for the vent. 2" will handle the bathroom group and kitchen sink. Even if you up-size to 3" at the roof for freezing issues, it's still considered a 2" vent - so that's fine.

BUT, you still need a 3" (or 4") vent somewhere in the system. The main stack/vent needs to match the outgoing main drain size.
 
 

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