Replacing double sanitary tee in back to back wc installation

[Skudbilt]

hello- I am planning to replace the old cast iron drainage for a back to back wc installation from the 60’s in Rhode Island. It’s currently a double sanitary tee with closet flanges 32 inches apart on center, with a 4 inch vent running up through the roof. The old style toilets currently in use work ok, but a couple fresh Toto units won’t. I don’t have enough vertical room to use a double wye. Is the drawn plan below acceptable?
Thanks for any comments or help. Apologies if this has been covered elsewhere, but didn’t see it, so please post a link.

 

[WorthFlorida]

I'm not a plumber and a member since 2009 I've learned a lot but venting I still have a hard time with. Hopefully my little modification would work better. Your probably will work but local codes can get finicky. You can go to your building dept and ask there. They are us very receptive to help. I'm surprised no one has yet answered this.

How To Vent & Plumb A Toilet (1 Easy Pattern) - Hammerpedia

Learn an easy way to vent a toilet using just a few basic DWV fittings...You'll discover the Toilet Vent Size, Drain Size, and a few mistakes to avoid.

www.hammerpedia.com

How To Plumb a Bathroom (with multiple plumbing diagrams) - Hammerpedia

See the drains & vents come together inside this bathroom. Includes pipe sizes for both major U.S. Plumbing Codes (IPC and UPC).

www.hammerpedia.com

 

[Sponsor]

 

[wwhitney]

Rhode Island uses the IPC, which permit horizontal wet venting for up to 2 bathroom groups. So one dry vented WC can wet vent the other WC, and the layout in the OP is allowed.

The layout in post #2 may be considered better, in that it dry vents both WCs, but it violates the rule on not connecting vents at an elevation below 6" above the fixture flood rims. So the two dry vents would need to ascend in parallel until 6" above both bowls before they combine.

Chapter 9 Vents: Vents, 2021 Rhode Island Plumbing Code | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Cheers, Wayne

 

[Skudbilt]

Thanks for your responses.
While I’d like to vent the toilets separately, the floor joists (not shown in drawing) prevent there being enough vertical room to accommodate. Also, the 4 inch vent is existing and I’d like to avoid opening walls if possible.
Last, I’m concerned about tying in the sinks/showers downstream of the two toilets (why im planning to put tee above middle combo to pick them up)- all in all it’s a shoehorn and this seemed like least amount of fittings and minimal shenanigans.
Looking forward to new toilets. Thanks for the help.