Proper fitting to turn a stack horizontal below slab
I had to cut a new footer into my basement floor during a reno I'm currently doing on my house, and the drain stack runs through the new footer. We're checking with the structural engineer to be sure that it can be encased in the footer, but in the meantime I'm replacing the old cast line with PVC. The original CI stack was cut off about 2 feet above the floor a few years ago when I replaced the entire drain/vent stack other than the underground. I'm now replacing from there down to the ground and horizontally through the area of the new footer to prepare for the pipe to be buried in concrete.
I know that you can typically turn a vertical drain horizontal with a regular 90 (not the tight turn vent 90, but a medium or long sweep). I was just wondering if the same applies for the bottom of the stack where it turns horizontal, or does this application require 2 45's? One of my plumbers told me that you can't offset the stack with greater than 45s (other than above the highest drain fixture), so wanted to be sure the standard 4" 90 would be an acceptable turn at the base.
The old CI stack had a cleanout near the floor, which was why we cut 2' up (no good place to fernco on due to the fittings). We put another cleanout right away on the new PVC stack, which is 27" above the floor. Now the lower CI cleanout is gone, and I think the PVC cleanout is higher than usual. Do I need to cut it out and lower it, or can I just pipe down from it and leave it where it is? What is the normal height to put the cleanout?
See attached pictures.
Below you can see the CI section being replaced, with the old cleanout near the floor. Do I need to lower the PVC cleanout, or is the current 27" to center of cleanout ok? If it needs to be lowered, what is standard height?
The plan is to couple on to the PVC stub currently in the fernco with 3" PVC, bring it down to the 4" elbow with a 4x3 bushing in the top of it, then run 4" over to the edge of the opening, where a 4" banded fernco will be installed in the dirt just past the footer (so you can get to the fernco to replace the CI at a later date w/o cutting into the footer, if that becomes necessary). Is this elbow the proper/best way to go, or should it be done with 2 45s to ease the turn even more? The new elbow has a slightly longer sweep than the original CI one. Its a Nibco 4807 4" 90. The current setup has been working perfectly for several years now, so doesn't seem to be causing any slow-downs.
Sorry for the small pictures... originals were too big to upload, and I don't have good software to resize them, so had to use the thumbnail shots.