Drain/Vent for New Bathtub

[Construction_Zone]

First time poster here. I stumbled on this website soon after I bought my house over a year ago and every time I "googled" a question I had about plumbing, I would find a good answer or discussion here. So thank you for that. But to the point, I am renovating the downstairs bathroom (it's currently a half bathroom) and adding in a claw foot bathtub. I plan on gutting the old bathroom, increasing its size, and breaking out the concrete slab to relay the original piping (60+ year old cast iron) and add in the bathtub drainage. I think I have a good handle on the new drainage/venting of the new setup, but I wanted some feedback from some of the more experienced plumbers/DIYers. Attached are two sketches, one being a profile view and the other an isometric that show the new layout. My town has adopted the ICC NY state plumbing code, which is basically the IRC.

I plan on oversizing the drain pipes since it will be wet venting the bathtub and because they will be buried in concrete so I will never see them again (I hope!). I will also install 2 clean outs: 1 starting at the sink that will reach the main soil stack, and 1 in the wall behind the toilet that will reach the bathtub.

I have not submitted anything to the town's AHJ yet, I'm just trying to get feedback on the new setup since I'm still in the planning/design phase of the project.

 

[Cacher_Chick]

Some codes will allow the entire bath group to be vented by the 1.5", while others will require 2".
I would not increase the horizontal drain size to 3" until the wye for the WC. The lesser fixtures alone cannot scour the 3" pipe.
All connections on the horizontal must be wyes. All connections on the vertical must be sanitary tees.

 

[Sponsor]

 

[Construction_Zone]

Thanks cacher for the response. Thats a good point about the 3" pipe between the tub and WC not being able to properly scour since flow rate will be decreased. The 1.5" VTR is galvanized steel that goes through the second story walls and up through the roof, which makes it difficult to replace, but according to code:

"916.1 Size of stack vents and vent stacks. The minimum required diameter of stack vents and vent stacks shall be determined from the developed length and the total of drainage fixture units connected thereto in accordance with Table 916.1, but in no case shall the diameter be less than one-half the diameter of the drain served or less than 11/4 inches (32 mm)."

Table 916.1 allows 27 feet of developed length at 1.5" with a drain diameter of 3" as long as the DFU is less than 53. So I think it is OK per code.

 

[Construction_Zone]

The project is under way and i made some changes to the plumbing since I realized there isnt enough room for a tub. Now I will be installing a shower with its own vent (no longer wet venting). Also after reading a post few posts about a 2" inlet heel on the back of a closet bend isnt a good idea, i modified to make the sink/shower connection downstream from W.C. Additionally, after digging up the slab i found the old fitting leaving my house to be some time of 4" combo wye with a 3" inlet heel. I will be using a 4" combo wye with a 4" to 3" adapter. Any glaring issues?

Also some cracks formed on the slab that lead to the wall while i was hammering out the slab. (I used an impact hammer/driver to perferate the slab then hammer out). One crack is slightly elevated (1/16 or 1/32). Will this be a problem for tiling? I would like to use detra and I plan using self leveling compound as a base.