I am trying to remove an old shower base from my basement level bathroom. It's on a concrete slab and the drain goes down into the floor, no access from below. It's a 48 x 32 rectangle with the drain exactly in the center. Removing the grill exposes an opening where there appears to be lead securing the base to the waste pipe. There are no nuts or screws. I tried lifting it up but the drain has it securely fastened down.
How do I remove the old base?