HELP!! I bought a new bathroom vanity and had a plumber (?? ) to come and install the unit. I needed to build a half wall to accommodate this unit and some floor issues and so the plumber replumbed the supply lines on the wall and stubbed them out and they are galvanized. I built my wall around the supply lines and then started thinking about the drain and it is located in the floor. How do I get this unit set in place since the supply lines and drain are coming from different directions. Can I drill the drain pipe hole in the unit and reconnect the drain pipe after I have it set in place? All the drain piping is pvc pipe and the vanity is not one of those that comes clear down to the floor, it has an opening between the floor and the bottom of vanity.

the plumber replumbed the supply lines on the wall and stubbed them out and they are galvanized.
You just couldn't have contracted a licensed plumber to do your work. We haven't used galvanized pipes since the 60's.

the drain and it is located in the floor This is a illegal "S" trap, ( your plumber should have told you that).
We can not either advise or help you to install a plumbing fixture against code. Your vanity will have to be vented. My advice, Get a licensed plumber in to tell you how to install it by code. This will take the drain out of the floor and stub it out of the wall where it belongs. A vent will have to.be figured out. If local code permits a AAV, (air admittence valve) installed behind the trap (see image) would be your answer. Good luck, Tolm