When you buy a new dishwasher from a specialty outlet, the price often includes the delivery team making the hookups, and it may even include hauling away the old dishwasher. But if you buy the dishwasher from a big-box home improvement center or an on-line retailer, connecting the dishwasher is usually not included—or it may cost you a substantial additional fee to have this done.
Fortunately, connecting the dishwasher yourself is a fairly easy job, once the old dishwasher has been removed.
Three Mechanical Connections
Connecting a new dishwasher requires three connections: a power-cord connection, a water supply connection, and a drain line connection. DIYers can do all of these if they understand what's required.
The power connection may be the trickiest, especially if you don't have experience with electrical wiring. Dishwashers can be "hard-wired" with an NM circuit cable that feeds directly into the wire connection box on the dishwasher; or, more commonly, they can use a standard appliance cord that plugs into a wall outlet. Either way, the electrical code now requires that a dishwasher be served by its own dedicated circuit, and if yours is not wired this way, you may want to have a new circuit installed at the same time you are replacing the dishwasher. In some areas, code requires that the dishwasher must be plugged into an outlet. Even where not required, this is the better strategy, since it makes it easier to disconnect the appliance if it needs to be serviced in the future.
There is no reason you can't wire the dishwasher yourself. Both hard-wired connections and appliance cord connections are done exactly the same way, with wire connections made inside an access panel at the base of the appliance.
The water-supply connection is an easy matter of connecting one end of a braided steel supply tube to the water inlet valve on the dishwasher and the other end to a shut-off valve on a hot-water supply pipe. This supply tube is really nothing more than a longer version of the same kind of supply tubes that feed sink faucets and toilets, so if you've worked on those plumbing fixtures, you'll have no trouble with the dishwasher hookups. Hooking up the water supply tube to the dishwasher usually requires attaching a special brass fitting known as dishwasher 90—a 90-degree elbow that allows the supply tube to easily connect to the dishwasher. This fitting is normally included with the connection kit that also includes the braided steel supply tube.
Connecting the drain hose on a dishwasher is an equally simple plumbing job. The drain hose connects to the drain trap under your sink; on the way to the trap, it either loops up to the underside of the countertop under the sink or is attached to an air-gap fitting. The proper method of doing this depends on the code requirement in your area, but either method is intended to keep dirty wastewater from siphoning back into your dishwasher. As the drain hose loops back down, it is attached either to a nipple on the garbage disposal or directly to a nipple on the sink drain tailpiece.
Equipment / Tools
- Channel-lock pliers or adjustable wrench
- Drill and spade bit (where necessary)
- New dishwasher
- Dishwasher connector kit
- Pipe joint compound
- Electric appliance cord
- Wire connectors (wire nuts)
Attach the Electric Cord
Most of the working parts—both the electrical hookups and the plumbing connections—are located behind an access panel located on the front bottom of the dishwasher. While it is possible to make these connections while you crouch or lie on the floor, most people find it easiest to carefully lay the dishwasher on its back to remove the access panel and make the preliminary connections.
Start by removing the bottom access panel on the dishwasher. Visually identify the power cord connection fittings, the water inlet solenoid valve, and the drain fitting.
- Note: If there are not already access holes drilled in the side of the base cabinet, you will need to do this in order to run the power cord to the outlet and the drain hose to the garbage disposal or sink drain.
Remove the cover on the wire connection housing. Thread the power cord into the housing, and make the three wire connections: green wire from the appliance cord to the green grounding screw, white neutral wire to white dishwasher lead, and black hot wire to black dishwasher lead. These connections are normally made with twist-on wire connectors (wire nuts), but some appliances may have different methods. Replace the cover on the wire connection housing.
Hook Up the Water Supply
Your dishwasher connector kit includes a dishwasher 90 that will serve to connect the water supply to the dishwasher. Installing the dishwasher 90 is the first step to hooking up the water supply for your dishwasher.
Locate the water inlet fitting on the solenoid valve. Apply some pipe joint compound to the threads of the dishwasher 90 fitting, then thread it onto the solenoid valve. Tighten fully by hand, then tighten an additional 1/4 turn with channel-lock pliers or an adjustable wrench.
Attach Water Supply Line
The dishwasher connector kit also includes a braided steel water supply tube. Thread the coupling nut of the supply tube onto the dishwasher 90 fitting, and tighten with channel-lock pliers or an adjustable wrench. This is a compression fitting that does not require pipe joint compound. Be careful not to overtighten, as it is possible to strip the threads.
Position the Dishwasher
Turn the dishwasher right side up. Slide the dishwasher into place under the kitchen counter, feeding the power cord, the water supply tube, and the drain hose through the holes in the sidewall of the cabinet. Line the appliance up to the center of the opening without pushing it too far back.
Use the adjustable legs to raise and level the dishwasher, following the manufacturer's directions. You can unscrew the legs with pliers, if necessary, to bring the dishwasher up to counter height and level it.
Anchor the Dishwasher
When you are satisfied with the placement of the dishwasher you can fasten it into place. Open the dishwasher door to access the mounting brackets. Use the screws provided to fasten the brackets to the cabinet frame under the lip of the counter.
Connect the Water Supply Tube
Connect the end of the water supply tube to the water supply shut-off valve under the kitchen sink. (In a new installation, you many need to install this shutoff valve on the hot water pipe.)
Turn on the shutoff valve and check for leaks. Also look under the dishwasher to check for leaks at the other end of the supply tube, where it connects to the dishwasher 90 fitting. If you notice leaks at either location, gently tighten the fittings a little more.
Connect the Drain Hose
The rubber drain hose is usually already attached to the dishwasher. If not, it can be attached now using a hose clamp.
There are several possible configurations for the drain hose, depending on the configuration of your sink and local code requirements:
- The dishwasher drain hose can be attached to an air gap fitting mounted on the countertop or sink deck. This fitting introduces air in the drain hose to prevent wastewater from being siphoned back into the dishwasher. From the air gap, a second hose runs to either a nipple on the garbage disposal or to a side nipple on the sink drain tailpiece. The hose from the dishwasher is usually attached to the air gap with spring clip, while the hose connects to the garbage disposer with a hose clamp.
- The dishwasher drain hose may be looped up and secured to the underside of the countertop, then drop back down to connect to a nipple on the garbage disposal or to the sink drain tailpiece. This "high loop" serves the same function as an air gap—to prevent dirty water from siphoning back into the dishwasher. Local codes may not allow this method, however.
Test the Dishwasher
Plug in the dishwasher’s electric cord. Before putting the face-plate on the front of the dishwasher, test it by running the dishwasher through a full cycle. Make sure that fresh water is being taken in and that drain water is flowing properly, with no leaks at any of the connections.
The final step is to put the face-plate back on the bottom front of the dishwasher.