1.5" Vent for a Laundry Group?


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Old 10-17-07, 11:51 PM
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1.5" Vent for a Laundry Group?

Seems like a simple thing to look up, but I haven't found a clear answer in code books, on DIY, or anywhere else...

Can I use a 1.5" pipe to vent a laundry group (washer standpipe and laundry tub)?

Standpipe and trap are 2". Utility sink has a 1.5" trap. The vent will rise to the joist space, run horizontally for 7.5 feet where it will join a 2" branch vent that serves a bathroom group, and continue on to join the house's 2" stack vent. For zone purposes, I'm in Maryland.

Thanks!
 
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Old 10-18-07, 09:46 AM
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Yes, 1 1/2" has plenty of vent capacity for a washer drain and a utility sink. Separate calcs are done for drain sizing and vent sizing and are based on 'fixture units' that are being served. Taunton Press has a 'Codecheck Plumbing' book available at the box stores or Amazon that has this info. Good refernce material.
 
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Old 10-18-07, 11:47 AM
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Thanks for the peace of mind. Unless I notch a joist, I really only have room to squeeze a 1.5" pipe between an I-beam and a duct.

I did read in my IRC book that the group is rated at 3 fixture units and that a 1.5" vent on a 2" drain can certainly handle this, but I think my wet/common vent setup was nagging me in the back of my mind. It wasn't until I started putting it all into writing that I realized what my problem is.

Thanks again!
 
 

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