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What determines # of plumbing roof vents?

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What determines # of plumbing roof vents required for a home?
asked in Plumbing by pattecakes (120 points)
edited by darekrudy
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1 Answer

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Hi one more time,


I can only blame my previous answer on the holiday season and too much work smiley.
I apologize for my answer that wasn’t really answering your question. By now you probably researched the plumbing vent subject very well so I will be most likely repeating that information.
The general rule is that every single plumbing fixture equipped with a trap requires venting, and its purpose (plumbing vent’s purpose) is to protect those traps from the atmospheric pressure differentials that could result in their siphoning or blowing out. If this happens, the sewer gasses could enter your house.
How do you connect those vents together and create a single stack or multiple vent stacks that will penetrate your house roof is regulated by a code adopted in your particular jurisdiction. The two codes that control plumbing vents are the IRC (International Residential Code) and the UPC (Uniform Plumbing Code), and unfortunately they have very different approaches to venting.
You’d have to find out what is enforced in your area and proceed accordingly.
This is a link to the plumbing section of IRC (called IPC – International Plumbing Code) - http://publicecodes.cyberregs.com/icod/ipc/2009/icod_ipc_2009_9_sec001.htm
The UPC is not available online, you would have to purchase it.
The main difference between the two codes is that UPC requires all vents to terminate through the roof, while IRC requires only one vent to terminate above the roof.
answered by darekrudy (21,730 points)
edited by darekrudy