Can I split then recombine vent line to minimize notch size through top-plate

[Billy1707]

To minimize notch depth through a top-plate, can I split a vertical vent line into two smaller lines and then recombine on the other side of the top-plate? For instance, 2in DWV line-> 2"x1.5"x1.5" wye-> 1pc 1.5" street 45-> 2pcs 1.5" DWV parallel through notched top-plate (properly strapped, of course)-> 1pc 1.5" street 45-> inverted 2"x1.5"x1.5" wye-> 2in DWV...?

 

[Jeff H Young]

Ive never heard of a code that requires a 2 inch pipe to be reduced to multiple smaller pipes . if code calls for a 2 inch pipe and reduce it to several smaller ones then you have violated code. will it work? yes , legal no. a single 1 1/2 might even work fine but thats wrong too

 

[Sponsor]

 

[wwhitney]

What size is the plate? Presumably a 2x4, as a 2x6 is 5.5", so you could drill a 2.75" hole for a 2" vent and stay under 50% of the plate width.

With a 3.5" wide plate, I don't see much advantage to (2) 2" holes over a single 2.5" hole. You're going to need to strap the top plate anyway. A hole would be better than a notch, I think.

Cheers, Wayne

 

[John Gayewski]

Yes you can the cross sectional area had been met. As ti weather the plan it a good on or not would probably depend. I don't see how taking out more of the wood would be better. I also agree a hole is better than a notch.

 

[Jeff H Young]

UPC has a minmum vent size on w/c of 2 inch which dosent mean crossection it means a pipe no smaller than 2 inch .
So if he is another code like IPC its possible he might meet code. I would expect a problem with inspection in UPC

 

[Reach4]

It's' not UPC.

Billy1701, whatever size pipe you go with, you could use shielded (banded) couplers to switch to copper for the trip thru the top plate. Copper OD is the nominal size + 1/8. So your holes are about 3/8 smaller diameter.

I know somebody whose plumber (with knowledge and agreement of my friend) ran 2 inch pvc to the floor and joined existing 1-1/2 inch vent for the trip to the attic. You could not tell it was not 2 inch from the basement. Air is pretty fluid. I am not a plumber.