Horizontal Wye - angle of branch

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Hi there,
I'm laying out a bathroom sewer, I have a few wyes connecting sewer branches as well as vent branches.
I know that the slope of the run needs to be 1/4"/ft.
My question is, does the branch of the wye need to be turned up (22, 45, 60) and then rolled in the direction of the next fixture (then raising 1/4"/ft)? Like this...

Or does the branch wye just need to continue the same 1/4"/ft, essentially keeping the branches of the wye at the same elevation? Like this...

Also, would the answer be different for a wye that is connecting a vent to a sewer vs a sewer to sewer?

A plumber friend told me I need to have the branch roll up, but I have been unable to find anything in the CA plumber code that specifies that. And my searching of the internet has not given me anything definitive either.

I'm asking because I don't have a whole lot of vertical room between where the sewer exits the building and where the top of the finished floor will be, so every vertical inch counts!

Here's what I'm trying to achieve...


(from top to bottom)
2" Shower vent
2" shower p-trap
3" main (exit on left, clean-out top right)
2" toilet vent
3" toilet
2" lav drain (with 1.5" vent - no pictured)

Jeff H Young

In the Trades
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lay the wye horrizonal with 1/4 per ft fall and make sure branch is rolled up at a 1/4 per ft min. your plumber freind would only be correct when speaking of a wye that serves as a dry vent below the flood level . but general drain piping has no need at all to roll up the why but it can be used at your convieniance when horrizontal wet venting the trap arms must not roll up
1 shower vent illegal if it is horrizontal as it appears
2 shower p trap good
3 main clean out
4 toilet vent illegal its flat
5 toile is fine
6 lav drain good
You might concider changing plan to a simple horrizontal wet vent in this case using the lav
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