How to Install a Dishwasher

The dishwasher is one of the many hardworking appliances in the kitchen that we tend to take for granted. For many of us, a few minutes filling the dishwasher is preferable to a half an hour in front of a soapy sink. So, when the dishwasher needs to be replaced, it might be a relief to know that installing a new dishwasher is one of those home improvement projects you can do yourself (with a little help.)

How Hard Is it to Install a Dishwasher?

The process is relatively straightforward when it comes to how to install a dishwasher. If you’re new to these kinds of projects, it’s a good idea to block off about 2 to 4 hours for dishwasher installation, because it can be difficult to reach some fixtures and working with larger appliances can require working on the ground and around fixed objects and small spaces. It’s also important to keep in mind that a dishwasher can be bulky or heavy and should always be moved carefully and with help from another adult.

Different dishwashers may require specific methods for handling the more challenging aspects of connecting wiring or installing plumbing fixtures in complicated locations. For instance, some models rely on aluminum wiring rather than traditional copper wiring, which can be complicated to work with, and you should plan on consulting with an electrician or having the dishwasher installed professionally. If the dishwasher installation project looks out of your do-it-yourself know-how, consult the professionals.

Before You Begin Installing A New Dishwasher

As with any home improvement project, it’s a good idea to plan ahead. Before you purchase the dishwasher, know what kind of space the dishwasher will need and be sure the measurements fit your kitchen. Countertop dishwashers are a good fit for a smaller kitchenette or an office breakroom, while full console dishwashers will need to be installed under the counter as a built-in dishwasher.

Once it’s time to install the new dishwasher, there are certain steps that you can take right up front to make the entire process easier. The first is to make sure that you have everything you need to install the dishwasher within easy reach of your work area.

Materials

• Wire nuts
• Hose clamps
• Electrical tape
• Built-in dishwasher

Dishwasher parts often sold separately:

• Copper supply line
• Dishwasher 90-degree elbow fitting

Tools

• Pliers
• Electrical wire strippers
• Adjustable wrench
• Power drill & bits
• Screwdriver
• Hole saw
• Level
• Safety glasses

Check the Instruction Manual.

Read the instructions about the new dishwasher that were provided by the manufacturer. There may be specific preparation steps or additional parts that you’ll need to be aware of before starting the dishwasher installation. Not all additional parts are included in the dishwasher purchase, so read the manufacturer's manual to be sure there won’t be any extra delays for ordering missing parts.

Make Sure There Is Access to the Required Power Supply.

Most dishwashers will require a GFCI-protected, 120-volt electrical outlet. If there isn’t one already installed at the dishwasher location, you may need to call in an electrician to install one prior to placing a new dishwasher.

Verify the Dishwasher Sizes.

Make sure that the new dishwasher is the same size as the old one. Most dishwasher sizes will be approximately 24” wide and designed for countertop depth at 24” deep and between 34” and 36” high. If the new dishwasher will be placed in the same cabinet space, it must have similar height, width, and depth dimensions to ensure it will fit the design of the kitchen. Also check the measurements against the kitchen layout to be certain that the door can open completely without interfering with walkways, doors, or drawers.

Double Check the Cabinets

Check to be sure the cabinet that separates the kitchen sink cupboard space from the dishwasher has the appropriately sized holes already drilled through to allow the connections, whether the supply hoses or the electrical cable. The hoses and their connectors both must fit through the holes in the cupboard sidewall, which could mean making them bigger or adding additional holes for the new hoses. If the holes aren’t already in place to install the supply lines between the dishwasher and the sink, use a hole-saw to bore holes along the back upper corner of the cabinet.

Have the Right Parts Ready.

Have all required cables and hoses on hand. Do not reuse the water supply or drain lines from the old dishwasher. For many models, the electrical cable can be kept for use with the new dishwasher unit.

Before reusing the power cord, make sure the units are compatible and that there is no damage to the cable or wiring.

Dishwasher Air Gap

The dishwasher air gap is used when connecting the dishwasher to the garbage disposal drain, to prevent backflow into or from the dishwasher. Check local codes to determine if your area requires an air gap for the dishwasher installation. Air gaps are installed into the kitchen sink or countertop and must be purchased separately for most dishwasher models.

The air gap is designed to connect to the dishwasher drain and then to the sink or garbage disposal connection inlet. The air gap is usually installed into the top edge of the sink or nearby countertop, which could require punching a pre-existing hole through the sink rim or boring a new hole through either the sink or the countertop. Again, call in a plumber or other contractor if you’re dealing with a more complicated project.

If local codes don’t require an air gap, simply mount the drain hose to the cabinet wall or underside of the countertop or sink with a high arc. Always keep the line free of sharp twists or kinks that could prevent the water movement and lead to leaks and water damage.

Getting Started

Once you’re ready to begin the dishwasher installation, the first step is to prepare the area you’ll be working in. Here are a few steps to take to make it easier and safer to work:

• Remove the cabinet doors in the area under the sink where you will be working. This makes it easier to move around and saves some time and effort over the course of the installation.
• Turn off the water supply at the shut off valve. Usually you’ll find the valve under the kitchen sink, next to or near to the dishwasher.
• Shut off the power to the kitchen at the breaker box. The breaker box is usually found outside the home, such as in the garage or basement.
• Always test that the electric is shut off before beginning any work with electrical wiring.

Depending on the type of countertops in your kitchen, it may also be useful to loosen the countertop if possible. This can help to avoid damaging the countertop with the dishwasher removal and placement. This isn’t always feasible, however, so there are other options to help safely fit the dishwasher in place that will be covered in another section.

Remove the Old Dishwasher

Before the new dishwasher can be brought in, you’ll probably need to remove the old one. This should be relatively easy and is a good primer for the steps required for dishwasher installation. Before you begin, be sure to dry out the dishwasher interior as much as possible to prevent trailing water when it’s moved away.

1. Remove the front access panel cover. This panel is located at the bottom of the unit, under the door. The connections for the power cord and the water supply line are run under the dishwasher unit and attached at the front. Use a voltage tester to be sure the power is off.
2. Disconnect the power cord. This requires separating the wiring from a heavy-duty appliance power cord, at the terminal box in one corner of the front access panel. This will consist of a neutral wire, a grounding wire (usually copper, with a green wrap,) and a hot wire. Untwist them or cut them using wire strippers.
3. Disconnect the water supply line from the front access panel. Water will leak, so have towels or a bucket at hand to protect the cabinet and floor.
4. Disconnect the drain hose from under the sink and allow it to drain any left-over water into a bucket. Be careful when removing the dishwasher as the drain hose will be pulled loose with the appliance. Discard the used drain hose.
5. Remove the screws from the anchor brackets that connect the dishwasher to the underside of the countertop and side cabinets, as needed.
6. Lower the leveling feet supports under the dishwasher in order to make sure there is plenty of clearance to remove the dishwasher without damaging the floor or the countertop.
7. Lay down cardboard, drop cloths, or thick rugs or towels, in order to protect the floor. Remove the dishwasher from under the cabinetry and set it on the cardboard or towels before sliding it away.

Prepare the New Dishwasher

Once you unpack the new dishwasher, make sure all parts are accounted for, it will need to be hooked up to the power and plumbing before it can be fit into place.

The easiest way to do this is to tip the dishwasher back onto cardboard, drop cloths, or towels on the floor near the dishwasher installation. This protects the floor from any scrapes and allows easier access to the dishwasher connection points located under and at the front of the dishwasher. There may be some water left from the testing of the machine before shipping, so plan to dry the inside of the tub or the floor if it spills.

Install or adjust the leveling feet at the four corners. Note if the rear corners have wheels, as the wheels may need locked or shimmed into place when the dishwasher is installed.

Next, remove the front access panel. From there, attach the 90-degree elbow fitting to the dishwasher valve. A wrench will be needed to make sure the piece is fit tight and secured against leaks before the water supply line can be attached.

To connect the power, you’ll need to have access to the front panel, and a clear view of the wires. Feed the cord through the hole in the cabinet to make sure the cord is long enough to clear the distance between the electrical outlet and the terminal box at the front of the dishwasher. (Do not work with the heavy-duty appliance cord plugged into the wall, just make sure it can easily and safely reach.) The terminal box inside the front access panel houses the three wires that attach to the cable.

Once the cable is fit through the cabinet wall, you can connect the electrical wiring per the manufacturer’s instructions. Generally, this should mean connecting wires to their matching color wires. Use wire nuts to twist them together and electrical tape to help secure them. The copper grounding wire should be attached to the green screw somewhere in the frame of the dishwasher terminal box.

Some dishwasher models have grooved sections along the bottom of the unit to house the water supply hose and power cord to help prevent kinks and tangles that can damage the appliance. If your dishwasher has these groves, rest the cable and hose in place once they are connected before you set the dishwasher upright.

Prepare the Plumbing

With the dishwasher unit ready to go, it’s time to prepare the plumbing under the sink.  

1. Disconnect the old supply line from the sink.
2. Feed the new copper water supply line through the cabinet to connect to the hot water supply shut-off valve.
3. Tape the supply hose connection down to the floor so that it will stay in place when the dishwasher is moved and will not get pulled back through the cabinet or slip out of reach. Line the hose up with the grooved section on the dishwasher base if the model has a specific line for the supply hose.
4. Disconnect the old drain hose from the sink or garbage disposal unit. Do not reuse the drain hose between dishwashers. There will be water in the drain hose, so have towels or a bucket at hand to catch the water.
5. Feed the new drain hose through the cabinet.
6. If there is no air gap, make sure there is a high arc in the hose, either by sending it through a hole bored in a high corner, or by mounting it to the wall to keep it in place arch the drain hose higher than the drain inlet to prevent drain backwash. Attach the hose securely to the cabinets or countertop to help it stay in place at the required height of 32” from the floor, being careful not to allow a kink to form in the hose.
7. Attach the new drain hose to the air gap, sink tail pipe, or the disposal connection. Use a constant tension hose clamp to hold it in place and secure against leaks.
8. Tape the drain hose to the floor so it does not move out of reach when the dishwasher is installed.

How to Install A Dishwasher

Now that the connections have all been prepared, the dishwasher can be installed in the cabinet space for the final steps.

1. Stand the dishwasher upright and place it near or partially inside the cabinet space under the countertop. Make sure the hoses and power cord are accessible and can reach their connections at the front of the dishwasher.
2. Connect the copper water supply line to the elbow fitting, being careful not to misalign the threads or overtighten the connecting bolt, to prevent leaks.
3. Connect the drain hose according to the manufacturer’s instructions. Dishwasher drain hose installation may require fitting the hose under the dishwasher or into one of the sides, depending on the model, so allow yourself room to access the connection.
4. Turn on the water supply to check for leaks along the supply line and at the connection points.

Test the Dishwasher

Once you’re certain the connections are secure and there are no leaks, turn on the electrical at the breaker box. Do not put the appliance under the countertop yet. First, do a test run of the dishwasher to make sure there are no leaks and all connections are operational.

Complete Dishwasher Installation

With the new dishwasher fully operational, free of leaks or other problems, it can be set fully into its permanent home under the countertop. Set the dishwasher front panels flush with the cabinet fronts and inset from the countertop edge to make sure it stays out of the way.

Use a level to be sure the appliance sits flat to avoid drainage problems on an uneven surface. This may mean reaching under the dishwasher to adjust the leveling feet a few times until it sits completely level.

It’s important to make these adjustments with the dishwasher in its permanent position so that the appliance can be adjusted to the floor grade exactly. The floor height and grade can be uneven if the floor under the cabinet space is finished differently than the rest of the kitchen, such as older linoleum or tile kitchen floors as compared to bare flooring under the cabinets.

If the dishwasher has rear wheels, set shims under or in front of the wheels to prevent them from moving while the dishwasher is operating. The shims should be mounted to the floor directly to keep them in place.

Finally, use the brackets to mount the dishwasher to the cabinetry as outlined in the manufacturer’s instructions. The last step is to replace the front access panel