How To Add a New Dishwasher to a Kitchen

Adding a dishwasher to your kitchen saves time and effort in your daily routine. Luckily, it’s a manageable project for homeowners with basic plumbing skills. In this guide, This Old House plumbing and heating expert Richard Trethewey walks you through the process of installing a new dishwasher. 

Preparing for Dishwasher Installation

Before you install your new dishwasher, make sure you have these tools and materials:

• Adjustable wrench
• Dishwasher tailpiece
• Drill/driver
• Drop cloths
• Electrical tape
• Open-ended wrench
• Pliers
• Polarized appliance plug
• Stainless steel braided water supply hose
• Teflon tape
• Three-way shut-off valve
• Twist-on wire connectors

Shutting Off Water and Power

Always take the following safety precautions when working with plumbing and electrical connections in your kichen.

1. Locate the main water shut-off valve and turn it off to stop water flow to the kitchen.
2. Switch off the power to the kitchen on your home’s electrical panel.
3. Verify that both water and electricity are off before moving forward with the installation.

Preparing the Space

The space where you’ll install the dishwasher should be clear. Remove any existing cabinetry if necessary and check that the dimensions of the opening match the specifications of your new dishwasher. 

Installing Your New Dishwasher

Once your space is ready, follow these steps to install your new dishwasher.

Set Up the Water Supply

Your first several steps will involve setting up the water supply for your dishwasher. You may not need to follow all these steps if you’re replacing an existing dishwasher:

1. Use a wrench to remove the existing shut-off valve on the hot water supply line under the sink.
2. Install a new three-way shut-off valve onto the existing hot water supply line. Having separate valves for each fixture is helpful if you need to turn off the water to one for maintenance.
3. Reconnect the hot water supply line to the new shut-off valve. Trethewey makes a compression connection using a ferrule and a nut.
4. Connect a stainless steel braided water supply hose to the shut-off valve.
5. Remove the existing tailpiece attached to the sink’s basket strainer and replace it with a dishwasher tailpiece. Tighten the threaded connections with pliers.

Make the Dishwasher Connections

Next, make the plumbing and electrical connections:

1. Tip over the dishwasher and lay it on its back on top of a canvas tarp.
2. Wrap Teflon tape around the male threads of a brass adapter elbow.
3. Thread the elbow into the water inlet port on the front of the dishwasher. Carefully tighten the elbow with an adjustable wrench.
4. Make the electrical connection to the dishwasher with a polarized appliance plug. Secure the wires with twist-on wire connectors.
5. Extend the stainless steel braided water supply hose from the sink cabinet out to the dishwasher. Tape the hose down to the floor with electrical tape.
6. Carefully slide the dishwasher into place.
7. Connect the water supply line to the dishwasher.

Secure the Dishwasher

Now you’re ready to secure the dishwasher in place. Here’s how Trethewey does it:

1. Use a drill/driver to screw the dishwasher’s mounting tabs to the underside of the countertop.
2. Adjust the leveling legs with a wrench until the dishwasher is perfectly level. Replace the dishwasher’s front panel.
3. From inside the sink cabinet, connect the discharge hose from the dishwasher to the dishwasher tailpiece. Secure the hose up as high as possible inside the cabinet to prevent contaminated sink water from backing up into your dishwasher.

Dishwasher: Testing and Finalizing

After installation, test your work and make any necessary adjustments.

Checking for Leaks

First, check for any obvious leaks:

1. Turn the water supply back on.
2. Carefully inspect all connections.
3. If you spot any leaks, tighten the connections or replace faulty parts as needed.

Running a Test Cycle

Next, run a test cycle with an empty dishwasher:

1. Plug in the dishwasher’s power cord.
2. Turn on the dishwasher and run a short cycle.
3. Monitor the dishwasher for proper operation and any unusual noises or leaks.

If all runs smoothly, you’re ready to start using your new dishwasher.

Tools: