Install the Sink. Assemble the faucet and drain on the sink before you install it on the vanity. Add a thin bead of silicone adhesive to the rim of the sink opening in the vanity. With the help of another person, carefully set the sink top on the vanity, making sure the plumbing is lined up.
If it is, you'll see a 2-inch plastic pipe stubbing out of the wall under the sink. To finish plumbing the sink drain, you have to connect it to that pipe via a P-trap.
Installation of bathroom sink plumbing proceeds in two phases.. a P-trap adapter, which coverts the pipe to a threaded compression connection that will hold a .