I'm in the process of considering a tub installation in a room that is a second floor laundry room in a historic house. This laundry room was the original second floor bathroom. Anyway, there is subway tile on all four walls, and there is a laundry sink in a position that could work to serve water and a drain for the tub in plan, but as it is the p-trap is 14" up from the floor where the tub would rest. Now, obviously I can remove some tile and lower the trap into the correct place, but I was wondering what would happen if the p-trap rose 14" to the drain? Would a tub full of water create enough pressure and suction to drain through? or would there always be a puddle remaining in the tub? Thanks

When you say "tub", you mean bath tub ? Or laundry tub ?

For laundry tub, drain is at correct height. For bath tub, P-trap has to go under floor. Otherwise, you'll have water standing inside the tub.

You can't raise the trap up over the tub drain, (see image). So if the trap's tight against the compression tee the tub will drain and not leave standing water in the tub. Since the trap can't raise any higher then the tee your questioon's moot. Regards, Tom