When I was renovating my bathroom I forgot to tell the plumber that I would also be renovating my basement down the line. When he installed the p trap under the tub, it sticks pretty far below the basement's ceiling height. I'd like to raise the trap up a little higher so I won't see it after dry walling.

Question:
How much of a vertical drop do I need from the bottom of the floor to the top of the p trap? Right now the distance is 7.5". The vertical drop from the bottom of the tub to the very bottom of the trap is 18". I'd like to cut it down to 9". Will this work? I'd like to shorten it by as much as possible to be able to fully hide the trap in the ceiling.

Right now the vertical drop from the bottom of the tub to the very bottom of the trap is 18". I'd like to cut it down to 9". Will this work? It should work OK. How much of a run do you have between your trap and where it connects to another pipe? How much pitch wioll that give you? Regards, Tom

There is a 3 foot run between the trap and the main waste pipe. In that 3 foot run, the vent pipe connects in about 2 feet away from the trap. Pitch is not a problem. Do you think I can move the top of the trap an inch away from the bottom of the floor?

There is a 3 foot run between the trap and the main waste pipe. In that 3 foot run, the vent pipe connects in about 2 feet away from the trap. Pitch is not a problem. Do you think I can move the top of the trap an inch away from the bottom of the floor?
You may have to cut the vent line back a inch as well but I believe you'll be OK raising the trap. Good luck and thank you for rating my answer. Tom

You have plenty of room to move it. Just cut the riser as needed.