Dishwashers can be awkward to install, because they fit tightly into a small space, hiding all of the complicated parts behind panels and doors. They also involve multiple connections for the water coming in and going out, plus the power that drives them.
Before you start, make sure you have the right cables and pipes: Most dishwashers come with the power cable and drain pipe, but not the water line that carries the water into it. You'll need to measure the distance from the water socket to the dishwasher inlet valve and get the right length of flexible pipe. You'll also need a 90-degree right-angle adapter that puts the pipe flat against the body of the dishwasher. Check the installation manual for the specific requirements of your model, but the input valve is usually a three-quarter-inch Garden Hose Type (GHT) connector. Both of these need to be rated for hot water.
Unpack your dishwasher
If the delivery people didn't do it for you, the first step is to unpack your new dishwasher. Most dishwashers come packed in a cardboard box with a wood or plastic packing base that helps protect the fragile parts in transit. Remove the straps that hold the box onto the packing base, then lift the box upwards to remove it. Next, you will have to lift the dishwasher off the packing base. Don't drag it off: You could end up damaging the parts on the base and make a mess of your floor. Instead, remove any retaining bolts and lift it off. Keep the box and packing base until you're sure the dishwasher is working properly, as you might need to use the box to ship it back if it's faulty.
Next, you'll need to figure out the kick plate, the panel below the door that covers the space at the bottom of the dishwasher. Some dishwashers will come with this already installed, while others ship it loose. Either way, you'll want it removed, as you'll need to get underneath the dishwasher later.
Don't be tempted to start unpacking the racks and trays on the inside of the dishwasher yet. It's best to leave them safely stowed for transport until the dishwasher is fully installed so they don't knock about and get damaged as you install the dishwasher. You should, however, open the door and make sure that the hinges and latch of the door are working properly. Put the dishwasher in front of the space that it will go into, but with enough space for you to get behind it.
Route the pipes and cables
Before you put the dishwasher in place, put the water and power cables through the hole in the cabinet space that feeds towards the power and water connections. Don't connect either end of them yet. Push the drain pipe through the same hole, but again, don't connect it. Most dishwashers will include several feet of drain pipe, but don't worry if this won't reach the drain that it will dump the water into: You'll have more pipe available when the dishwasher is in place.
To connect the right angle water pipe adapter, put a layer of teflon tape over the dishwasher input valve thread and screw on the right angle adapter until it's pointing in the direction that the water pipe is coming from, or the direction that the installation documents indicate. This should be hand-tight, don't use a wrench or clamp to tighten it any further.
Some dishwashers put the water and power connections on the back of the dishwasher body. Manufacturers such as Frigidaire use this approach. For these, you should connect the water line and power connections before you push the dishwasher into place. Others (like those from Samsung) put these connections on the front base of the dishwasher, right behind the kick plate. For these, you should push the cables under the dishwasher body, then push it into place and connect them after the dishwasher is fully installed.
Push the dishwasher in
To push the dishwasher into place, lift the front slightly and push it backwards. Many models have small wheels on the back that make this easier. Slowly push the dishwasher back into the space, making sure that none of the cladding that covers the dishwasher body or the cables are caught on the edges of the space. As you push, have a friend pull the pipes and cables through the hole so they don't get tangled behind the dishwasher.
Next, level the dishwasher. To do this, hold a bubble level against the top of the inside of the dishwasher and adjust the feet to make sure it is flat level left to right. Next, hold the same level against the front edge of the dishwasher and adjust both feet the same amount to level it top to bottom. This makes sure that the water can drain properly.
Once the dishwasher is level, secure it in place by drilling small holes in the surrounding wood through the holes in the mounting anchors that poke out from the top and sides of the dishwasher, and screw the included screws into these holes. This firmly anchors the dishwasher to the cabinet around it, so it won't move when the water sloshes around inside. Make sure the heads of these screws are flat against the anchor so that the door won't catch on them when it closes.
To install the water pipe, apply another layer of teflon tape to the thread of the right angle adapter, then connect the pipe to the thread of the right angle and turn it until it is hand-tight. Again, don't over-tighten it.
The drain of the dishwasher should be connected to the sink drain or waste disposal so that the waste water is dumped straight into the sink drain. Make sure that the drain pipe from the dishwasher is curved so that there is a good amount of it lifted above the drain connection. This prevents waste water from the sink draining into the dishwasher, a problem plumbers call backflow. Most dishwashers will include a clip or drain pipe holder to lift the drain pipe up. In some areas, you may have to install a device called an air gap that performs the same task: check your local plumbing codes for details.
The electrical connection will be inside a junction box that keeps water away from the cables. Remove the retaining screw on the cover, and feed the cable through the strain relief bracket. Connect the cables as per the installation instructions, and then tighten the strain relief bracket, so that if the cable gets pulled, it won't pull on the connectors. Finally, replace the junction box cover, making sure that no cables or connectors are trapped or pinched by the cover.
Next, connect the other end of the water line to the hot water valve, again applying teflon tape to the thread to make sure you get a good seal. Turn the water on, and check under the dishwasher for any leaks or drips. Even if it looks dry, leave the dishwasher for a few minutes and check again in case of a slow leak.
If there are no leaks, plug in the power cable and make sure that the dishwasher is getting power. Finally, you can install the kick plate to cover the space under the dishwasher. Now you can open the dishwasher, install the racks and trays, then run the dishwasher to test it out. If everything has been installed correctly, you should hear the dishwasher draw in water, swoosh it around and then eventually pump it out into the drain. Next, wash some dishes!