Which type of screed do you prefer?

Yes, you can definitely see the rubber rings on the clamps. If that has already been implemented, then "the child has already fallen into the well." I can't think of any standard off the top of my head where that is stated - sorry. Do you have underfloor heating in the technical room where the buffer tank is? Is there cement screed in the room where the buffer tank is?

Yes, you can definitely see the rubber parts on the clamps. If that has already been implemented, then "the child has already fallen into the well." I can't think of any standard off the top of my head that states this - sorry. Do you have underfloor heating in the technical room where the buffer tank is located? Is there cement screed in the room where the buffer tank is?

Cement sulfate screed. Underfloor heating is omitted at that spot. Clamps of the pipes see picture

The clamps are basically the right ones. So if there really are 9 cm of cement sulfate, then it should be able to carry and distribute the weight quite well. It's basically already half a floor slab. I would probably—also because it is "only" the technical room—grudgingly accept it if it has already been implemented. In the worst case, the joint of the base tiles breaks, and then you can tell your general contractor that in this case the argument about the maintenance joint doesn’t hold because EPS is not a compressive insulation material and he has accepted this in connection with the buffer tank. Then he should also renew the joint, done. But let's not philosophize about things that haven’t happened yet, straighten your crown and look ahead.