What Size of Waste Pipe for a Pedestal?

Pedestal Drain Pipe Set-up

• You do not normally see the drain pipes under a pedestal sink unless you look around to the backside of the pedestal. If you do look at a pedestal sink’s drain pipe set-up, you will notice that the set-up still uses a curving trap piece like that of any other sink. An elbow connects the end of the trap piece to the stub-out pipe in the bathroom wall, allowing the waste water from the sink to flow out of the bathroom.

Pedestal Sink Kits

• Some pedestal sink kits take the guesswork out of what size drain pipe you should use by including the needed drain pipe pieces. Just because the sink’s kit comes with all of the drain pipe pieces does not mean you do not need to trim the pipes so they fit correctly with the stub-out pipe in the bathroom wall. You must cut the pipes with a fine-tooth hacksaw so the ends of the pipes are not left sharp.

Tailpiece Size

• Even if your pedestal sink does not include a drain pipe assembly, it will include a tailpiece — a length of pipe that threads into the sink’s drain body. The sink’s pop-up stopper assembly inserts into the tailpiece through an opening, and the bottom of the stopper sits inside the tailpiece. The diameter of the sink’s tailpiece dictates the diameter of the drain pipe, since the drain pipe must thread onto the tailpiece.

Drain Pipe Placement

• The drain pipe for your pedestal sink sits inside the pedestal assembly. This means you cannot see the drain pipe if you look at the sink from the front, even if you stoop down to the level of the pedestal. If the stub-out pipe that is already in the bathroom wall does not sit high enough to sit inside the cavity in the sink’s pedestal, you must remove the old stub-out pipe and install one that is higher on the wall. Exactly how high the stub-out must be depends on the exact pedestal sink you choose, since different sinks require the stub-out to be at different heights on the bathroom wall. Moving the stub-out requires advance plumbing skills, so consider hiring a plumber to perform the work.