I am installing a new tub in an old house. This is a slab on grade structure and the tub drain connection out of the ground is copper. The plumbing from the tub is pvc, so the connection to the ground will be with a fermco (rubber sleeve w/stainless hose clamps) My question: This hole under the tub is a pathway for termites. I new houses, the contractors fill it with mortar/cement one the tub in installed. Here however, Im not sure I want cement/mortar in contact with the rubber and copper of the drainage system. How should I seal this hole?? Can that rubber connection between the copper and pvc be in contact with mortar and not degrade over time??