How to Install the P-Trap under a Sink
With your pedestal sink on the wall, you can install the P-trap. The U-shape of this pipe is the trap that retains enough water to prevent sewer gases from entering the bathroom. You can adjust the P-trap, sliding it up and down on the pipe that leaves the sink drain. The other end of the P-trap can slide into and out of the fitting on the wall.
If the P-trap doesn’t align with the drain that comes out of the wall, you may have to cut the tailpiece that protrudes from the pop-up assembly to install the P-trap.
Follow these steps to install the P-trap:
Slide the short side of the P-trap onto the tailpiece that drops down from the sink drain. Move the P-trap up or down to align the trap arm with the opening in the wall.
Use a hacksaw to cut the tailpiece if you can’t move the P-trap higher up the tailpiece and the trap arm is below the wall drain fitting. Purchase a longer tailpiece if the P-trap lies above the wall drain fitting when attached to the end of the tailpiece.
Take the lower part of the P-trap apart and insert the trap arm into the wall drain fitting as far as it will go.
Pull the trap arm out of the wall fitting until it lines up with the top U-shaped portion of the trap.
If the trap arm comes completely out of the wall before it can be attached to the trap, purchase a longer trap arm. If the trap arm is in the wall fitting as far as it will go and extends past the U-shaped part of the trap, cut it with a hacksaw.
Insert the trap arm back into the wall drain, move it into alignment with the trap, and thread on (but don’t tighten) the slip nut.
After you’ve joined the trap parts together, tighten the slip nuts on the tailpiece and the wall drain fittings.