I want to turn a half bath into a full bath in my basement. Currently the washer and dryer along with the water heater are in the half bath along with the commode and sink. I want to add a bath tub and the lay out of the room is such that the tub installation would probably require less work if it were placed where the sink is currently located and try to utilize the current sink drain. I was going to move the sink and vanity to where the washer and dryer currently are use the plumbing for the washer for the sink. My concern and question is this: The bath is on a slab and it appears that the upstairs sink shares the drain pipe for the downstairs sink. Should I build a small riser to place the tub on to accommodate the drain and if I try to use the drain the sink is currently using, will there be a drainage problem from the upstairs sink? Would it be better to cut a channel in the slab to install the tub drain than to try to build that small riser?

I can’t see the route of the drain because it disappears into the bottom plate that is sitting on the slab

Any suggestions?

If you can make it work you can connect the tub drain up in a space of about 2 1/2 inches about the concrete, so a riser would not have to be very high. All though the upstairs drain connected into the tub drain might not be up to code it will still work, there might be a chance of the trap water being sucked out of the trap and odor could escape but I think it would be worth a chance.