Wisconsin, double wye or double San tee??

[Concrete cowboy]

Hey everyone, I’m currently updating my plumbing and going to pvc. In the first picture I have 3inch cast that goes to 4 inch cast below. It looks like it has a 3” double San tee fitting up top for two toilets and a double wye that two sinks run into.

Would it be acceptable to keep everything the way it is or should I use another double San tee for the sinks?

The second picture is what I bought and was thinking about doing.

I am also going from a 1 1/2 to 2” pvc for the sinks.

Any advice would be much appreciated!

 

[Breplum]

Your CI double combo is ideal. to tie the sinks to the stack, tees are acceptable but the wye is fine as well.
Unshielded rubber couplings should not be used except in emergencies as they are not UPC approved for domestic drainage and reason is that they do not hold alignment well unless there is no stress (there is always stress, sooner or later).

 

[Sponsor]

 

[Concrete cowboy]

Is there a different type of coupling I could use to connect the cast with pvc? Otherwise I would need to replace the cast with pvc all the way up to the roof. The cast iron vent has a riser clamp on the main level (ranch house) and attic supporting the vent.