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jklingel 02-06-2014 01:00 AM

Vent bottleneck
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I may have made a mistake here. The picture shows a 2" sanitary T that catches a vent line from a bathroom (2 sinks, shower, toilet) and a vent line from a kitchen (coming from below) that has one sink and a dishwasher. The sanitary T is right at the ceiling, and will neck-up to a 4" vent pipe going through the roof in about a foot. In other words, there is about 8-10" of two inch pipe coming out of the san T and going up through the insulation, then entering a 4" vent pipe. The 4" line vents nothing else. There is 32" of cellulose on top of the plywood where the 2" sanitary T is. I have been told that the 2" san T should be 3". The questions then are (1) will this work? (2) Is it UPC compliant? (3) Is there any benefit, if it is marginal, to tying this line to another, exact set-up on the other side of the house? That way, both lines have access to two, 2" san T's. I'm pushing it here, I know, if not flat-out in error. Thanks. john

Alan 02-06-2014 09:10 AM

By my quick count, a 2" should be ok via UPC. It will take 24 fixture units as a vent.

A full bath and a kitchen should be no problem on that line.

The reason for upsizing at the roof is for snow/freezing.

Who told you that the 2" vent should be 3" ? Did they realize that it is already upsized going through the roof? Ask for a code reference requiring such.

TheEplumber 02-06-2014 12:22 PM

199 Attachment(s)
My version of UPC says my vents through the roof needs to equal the cross sectional area of the building drain. In your case that's 3" so all your vents combined need to equal 3" even though 2" will handle the fixtures served.
So yea- that would be a 3 x 2 tee

jklingel 02-06-2014 12:41 PM

OK. Thanks for the input. I thought the fitting needed to be 3", but I wanted to see if this would work. I don't know if I have the energy to tear into the ceiling and replace the 2" w/ a 3". I should....

jklingel 02-07-2014 01:07 AM

I think I have a possible solution that will be easier than tearing into the ceiling, removing the 2” san T's and jamming in 3”-2”-2” san T's (which I should have used in the first place). I can easily tie the North and South vent lines together, which will give me two, 2” san T's to vent through. Those in aggregate have just under a 3” fitting's cross-sectional area. Then, there is another bathroom on the South end that is not vented yet. For it, I can go right up through the roof with a 3-2-2 san T that will go up to a 3” vent pipe. From the middle of that T I will run a horizontal branch over to the South vent system that I just tied the North to. Thus, all three vent pipes will be tied together, and all fixtures will be tied to two, 2” san T's and one 3” san T all working together. This is very circuitous, and there will be some friction loss, but I think that this will work and may even be code compliant, albeit “not real professional”, or at least a professional who is thinking. Do you think this will be OK? Thanks again.

TheEplumber 02-07-2014 08:12 AM

199 Attachment(s)
2- 2" and 1- 11/2" vent will handle your huse

Alan 02-07-2014 09:32 AM

E-Plumber is right, but you didn't mention that you don't have any other vents in your house.

If that is the case, then you do need to upsize to 3" where the two 2" lines intersect.

jklingel 02-07-2014 01:03 PM


Originally Posted by Alan (Post 1302831)
E-Plumber is right, but you didn't mention that you don't have any other vents in your house.

If that is the case, then you do need to upsize to 3" where the two 2" lines intersect.

There are only the three vents; two, 2" san T's (which are only a few inches below the 4" vent pipes) and the one 3" san T that will go directly into a 3" vent pipe. I did not know to upsize the joining fitting to 3" (where the two, 2" lines will meet). I will do that. Thanks. This is one of the many cases in building where one tiny mistake leads to a lot of hassle. On my son's house, I will know better....

jklingel 02-09-2014 01:20 AM

Last question here. It was mentioned that where the two, 2" vent lines will join, what fitting do I need? The fitting will be horizontal, and at the ceiling. One end will catch a 2" line from the right, the other end a 2" line from the left, and the center will go to a 2" san T that then exits the building. Is a clean-out T OK? Double elbow? Double T-wye combo? Thanks.

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