Back to back toilets on vertical wet vent UPC

[Still_Learning]

Hi all! Wanted to get your thoughts on this diagram for a UPC compliance. I think the double wye is the best fitting for the back to back toilets based on other posts on this forum.

My main questions are:
1. Can I join the lavatory and shower before joining the main stack since there’s no fixtures above (therefore a dry vent)?

2. Does the wet vent work for the two toilets joining at the double wye?

Thanks in advance for any help you can provide

 

[wwhitney]

So what's venting the lavatory? The vent for a trap needs to connect within one pipe diameter of fall from the trap. So with the lav fixture drain dropping down to join the shower fixture drain, there's no way for the stack to vent it.

If you separately vent the lavatory (which could be reconnected to the stack at least 6" above the lavatory flood rim level), then your configuration is fine, assuming the resulting shower trap arm (from trap to wye with the lav) is no more than 60" and 2" of fall. The lav wet vents the shower horizontally, and the stack wet vents the WCs.

If you want everything to be vented by the stack, then each external trap (each fixture other than WCs) has to connect to the stack within one pipe diameter of fall. And has to be close enough to the stack--a 1-1/2" trap arm is limited to 42", a 2" trap arm is limited to 60".

Also, doesn't appear to be an issue in your diagram, but a WC fixture drain, measured starting at the closet flange, is limited to 72" in length before hitting a vent (the stack in this case).

Cheers, Wayne

 

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[Still_Learning]

Thanks @wwhitney ! I just looked and there is a vent for the lav so I should be good to go. Thanks for the additional things to look out for.