Denray Posted May 18, 2017 Report Share Posted May 18, 2017 Seems like this vent should not be reduced as it rises above the house, right? Quote Link to comment Share on other sites More sharing options...
Chad Fabry Posted May 18, 2017 Report Share Posted May 18, 2017 Where it freezes, the vent diameter must be at least three inches to prevent frost closure. I'm not bothered by the change in size and I couldn't find anything that prohibits it- if water is running down the pipe it flows from smaller to larger. What probably limits the size is the number of fixture units. If I'm right and that's 2-1/2 inch pipe, just 6 FU's are allowed. If it's 3-inch pipe 12 FU's are allowed and it's probably OK for any normal modest house. All that said, it probably works fine. Quote Link to comment Share on other sites More sharing options...
Denray Posted May 18, 2017 Author Report Share Posted May 18, 2017 Thanks! Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted May 18, 2017 Report Share Posted May 18, 2017 28 minutes ago, Chad Fabry said: Where it freezes, the vent diameter must be at least three inches to prevent frost closure. I'm not bothered by the change in size and I couldn't find anything that prohibits it- if water is running down the pipe it flows from smaller to larger. What probably limits the size is the number of fixture units. If I'm right and that's 2-1/2 inch pipe, just 6 FU's are allowed. If it's 3-inch pipe 12 FU's are allowed and it's probably OK for any normal modest house. All that said, it probably works fine. Chad, Probably should stick with the standard abbreviation D.F.U., well, cuz FU. 2 Quote Link to comment Share on other sites More sharing options...
Chad Fabry Posted May 18, 2017 Report Share Posted May 18, 2017 That was funny. Quote Link to comment Share on other sites More sharing options...
mjr6550 Posted May 22, 2017 Report Share Posted May 22, 2017 Regardless of freezing, I believe the IRC requires one minimum 3" vent. However, its an old house. I doubt I would have mentioned it. Quote Link to comment Share on other sites More sharing options...
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