How to Install a Washing Machine Outlet Box

Begin by selecting the ideal location for your washing machine outlet box. The standard height is typically between 42 and 48 inches from the floor to the top of the box. Use an electronic stud finder to locate the vertical wall studs. The box must be installed in the cavity between two studs. Once you've found a suitable bay, use a pencil and tape measure to mark the desired height. Also, identify the paths of the nearest hot and cold water supply lines and the main vertical drain stack you will be tying into. Planning these routes now will save significant time later.

Place the washing machine outlet box against the drywall at your marked location and trace the outline of the box's body (not the wider faceplate). Use a level to ensure your traced lines are perfectly straight. With a drywall saw, carefully cut along the pencil lines. Start with a shallow plunge to make sure the area is clear of obstructions. Once you've cut all four sides, gently remove the piece of drywall to reveal the wall cavity.

For a secure installation, you must add horizontal blocking. Measure the distance between the two vertical studs inside the wall cavity. Cut two pieces of 2x4 lumber to this length. Position one piece just above where the top of the box will be and the second piece just below the bottom. Secure these blocks by driving 3-inch wood screws at an angle through the ends of the blocks and into the studs (a technique called toe-nailing). These blocks will provide a solid surface to mount the outlet box.

This is a critical plumbing step. Locate the 2-inch PVC vertical drain stack you plan to connect to. Use a reciprocating saw or PVC pipe cutter to remove a section of the pipe where your new line will connect. Clean the cut ends. Apply PVC primer to the inside of a 2-inch PVC sanitary tee fitting and the outside of the pipe ends. Then, apply PVC cement over the primer and quickly push the pipe ends into the fitting with a quarter-turn motion to ensure a good seal. Run a new 2-inch PVC pipe from the sanitary tee to the outlet box location. Ensure the pipe has a constant downward slope of at least 1/4 inch for every foot of horizontal run to ensure proper drainage. You will likely need to install a P-trap assembly near the box connection point to block sewer gases, as per code.

First, SHUT OFF THE MAIN WATER SUPPLY to the house and open a nearby faucet to relieve pressure. Locate the nearest 1/2-inch hot and cold water lines. Assuming they are PEX, use a PEX cutter for a clean, square cut. Insert a 1/2-inch PEX tee fitting into each line. Slide a copper crimp ring over the pipe, push the fitting fully into place, and use a PEX crimping tool to secure the ring. Repeat for all three ends of both tees. From the open ends of the tees, run new lines of 1/2-inch red PEX (for hot) and blue PEX (for cold) up through the wall to the outlet box opening. Leave several inches of extra pipe extending into the opening.

Prepare the washing machine outlet box by removing the knockouts for the hot, cold, and drain connections. Feed the PEX pipes and the PVC drain pipe through the corresponding holes in the back of the box. Insert the box into the opening in the wall, pressing it firmly against the 2x4 blocking you installed. The front flange of the box should be flush with the face of the drywall. Secure the box to the blocking using the mounting clips or screws provided with the unit.

Cut the PEX pipes extending through the box so they are the correct length to connect to the valve inlets. Slide a 1/2-inch copper crimp ring onto the blue (cold) PEX pipe. Push the pipe fully onto the cold valve inlet (typically on the right). Position the crimp ring 1/8 to 1/4 inch from the end of the pipe and use the PEX crimping tool to compress the ring until it's secure. Repeat the process for the red (hot) PEX pipe on the hot valve inlet (typically on the left). For the drain, cut the 2-inch PVC pipe to the proper length and use PVC primer and cement to glue it into the drain port on the outlet box.

The moment of truth. Ensure the new hot and cold water valves on the outlet box are in the fully closed position. Go to the main water shutoff for the house and turn it on SLOWLY. Listen for the sound of rushing water, which should stop once the pipes are full. Return to the laundry room and use a flashlight to meticulously inspect every new joint and connection for any signs of moisture or dripping. Check the PEX tee fittings where you tapped into the main lines and the crimp connections on the back of the outlet box. If you see any leak, shut off the main water supply immediately and remake the faulty connection.