Cut into the existing waste line at the closest approach to the sink with a hacksaw. Remove a section large enough to accommodate a wye fitting with a 2-inch outlet. A wye is a drainage fitting shaped like a "T", but with a sweep inlet instead of a straight one. Glue in a plastic wye with PVC cement if the drain is PVC, being sure the inlet is facing the sink and has a slight upward tilt. If the drain is cast iron, attach a rubber wye to the pipes by tightening the metal straps on either end with a screwdriver.
Attach a small length of 2-inch PVC pipe to the wye outlet, either by gluing it in or tightening the metal strap on the wye with a screwdriver. Glue another wye to the pipe with the inlet facing up and toward the nearest vent attached to the existing drain line. Cut into the existing vent at a convenient location and install another wye with the inlet facing the first wye. Connect the two wyes with 2-inch PVC pipe, gluing the ends of the pipe to the wyes.
Glue a small length of 2-inch pipe to the other outlet of the wye, then glue on a 2-by-1 1/2-inch P-trap adapter. It has a compression fitting on the end so you can connect the 1 1/2-inch drain pipe from the sink.
Apply plumber's putty liberally to the underside of the strainer of a drain assembly and set the drain into the hole in the bottom of the sink. Screw the retaining nut on from underneath and tighten it with slip-lock pliers. The drain should have a length of 1 1/2-inch pipe extending down from it, called the tail piece.
Set the sink in position. Remove the nut and flange from a P-trap assembly and slide them up along the tailpiece. The nut should go first, with the threads facing downward, followed by the flange with the tapered end facing down. Slide the mouth of the trap up along the tailpiece so that the outlet of the assembly is high enough to provide a downward slope in the pipe that extends from the other end of the trap to the drain. Insert the flange in the opening and screw on the nut, tightening it by hand.
Assemble a length of 1 1/2-inch pipe that extends from the outlet of the P-trap to the drain, gluing in appropriate fittings as needed. Insert one end in the compression fitting on the end of the P-trap and the other in the adapter attached to the wye in the drain. Tighten both compression nuts by hand. Support the pipe, if needed, with plumbing straps.
Things You Will Need
- Wye fitting with 2-inch outlet
- PVC cement
- Two 2-inch wye fittings
- 2-inch PVC pipe
- 2-by-1/1/2-inch P-trap adapter
- Drain assembly
- Plumber's putty
- Slip-lock pliers
- P-trap assembly
- 1 1/2-inch PVC pipe
- Plumbing straps
- Check the level of the pipe that runs from the sink to the drain after you've installed it. Adjust the height of the mouth of the P-trap as needed to maintain a downward slope along the length of the pipe.
- P-trap compression fittings usually need only hand-tightening, but if any of them leak, tighten them more with slip-lock pliers. Don't over tighten, though, or you may strip the threads.