Rubber transition in sewer drain stone under slab
Hi! Glad to have found someone who is so knowledgeable about all things Plumbing.
My question is this: Yesterday our plumber installed the sewer drain in our stone. It will be for Kitchen/ bath/ utility which rests on a 4" slab. We are in Western New York, so it is all below the frost line. One of the drains to the kitchen sink was just a little off level because we moved the whole works a few inches and the plumber CUT the PVC 40 and put in a rubber & stainless couple. Then he used another of these transition pieces between the shower and the utility.
Is this rubber transition really a good idea?
It will be in stone, not concrete where it lies. He said there may still be ground water that gets past the tie-- so the trap box near the shower will later need to be filled with concrete too.
Will this stuff break down through contact with ground water or stone or the heat from the 1/2" radiant tubing I plan on running through the slab?
Am I too obsessive? It's my first house and I'm acting as GC. I have about two weeks to correct this if the rubber is too weird. Then it will sit there for the next 200 years.
Thanks in advance for your reply.