How to Plumb a Washing Machine Drain

Make sure the water from your washing machine ends up in a proper drain.

Washing machine drain lines are often simply placed over the edge of a sink, where they empty into the sink drain. But this practice is not approved by some building codes, and the machine drains directly into a drain line. This type of drainage can be achieved by adding a new standpipe drain to an existing wall-mounted sink drain line.

How to Plumb a Washing Machine Drain

Things you will need

  • Reciprocating saw
  • Y-connection PVC drain pipe sized for existing drain line
  • Utility knife
  • 90 degree PVC elbow
  • 2-inch diameter PVC standpipe drain (at least 36 inches long) with trap assembly
  • PVC Solvent Glue
  • Tube strap
  • 1/2 inch screws
  • 2-by-4 wood backing board (if needed)

How to Plumb a Washing Machine Drain

Step by Step

  1. Measure the PVC Y-Fitting to determine what length of pipe you need to remove from the existing drain line to insert the fitting. Mark this distance on the drain line, then make two cuts with the reciprocating saw to remove the old section. Make the cuts as straight as possible, perpendicular to the length of the pipe.
  2. Remove any burrs or rough edges from the cut ends of the drainpipe with the utility knife. Coat the inner surfaces of the two parallel ends of the Y-fitting with PVC solvent glue. Insert the cut ends of the drain pipe into the ends of the Y-fitting and push the fitting into place. Make sure the Y-fitting is oriented so that its third angled opening is flush with the drain tube, not above or below it. Let the PVC solvent glue dry completely.
  3. Coat the inside surface of the 90-degree PVC elbow with solvent glue, then push it over the remaining opening in the Y-fitting, orienting the open end of the elbow down toward the floor. Let the solvent glue dry completely.
  4. Coat the inner surfaces of the P-trap ends with solvent glue, then press one end onto the open end of the 90-degree elbow and the other end onto the PVC standpipe. The vertical column should be pointing up, parallel to the wall, and as close to the wall surface as possible.
  5. If the installed standpipe is too tall, use the reciprocating saw to cut it to the proper height. The top of the pipe must be higher than the highest water level in the washer, at least 34 inches from the floor.
  6. Wrap the pipe strap around the top of the standpipe and attach it to the wall with 1/2-inch screws. If the room is not finished, run a 2-by-4 wood backing plate across the exposed studs, then attach the pipe strap to the backing plate.
  7. Hook the washer’s rubber drain hose onto the open top of the standpipe.

Tips and Warnings

You may want to dry-fit the Y-fitting, elbow, trap, and standpipe before gluing to ensure they fit properly. Once the solvent glue dries, the connections cannot be loosened, moved, or tightened.
Check local plumbing codes before starting work and obtain any necessary permits.