How to install dishwasher air gap
Things You'll Need
Measure the space where you want to install the LG dishwasher to make sure that it meets the available space requirements. Depending on your LG model, your dishwasher will need a certain amount of clearance on the side to be able to operate properly. The exact dimensions will be given in the owner's manual that came with your unit.
Prepare the electrical connection. LG dishwashers should operate on their own circuit. If you do not have a free one at the main panel, have a certified electrician install one for you. You should have at least four feet of wire free at the end of the line where the dishwasher will be installed.
Prepare the water connections. LG dishwashers work best when connected to a hot water supply. Turn off the water supply at the dual supply valve. If you do not have a dual supply valve, you will have to install one. Be sure to turn off the main water supply while you are working. Connect the water supply hose with the proper compression fitting. Use plumber's tape to ensure a air tight connection.
Maneuver the LG dishwasher adjacent to the place where it is being installed. Check for any damage. Remove any protective shipping packaging or screws. Remove the bottom panel from the machine.
Move the LG dishwasher to it's final installation
location, beneath the countertop. Adjust the feet at the bottom of the machine to ensure that it's level.
Connect the water supply to the dishwasher. Wrap the threads on an 90-degree elbow inlet in plumber's tape and screw this into the water inlet. Pull the water supply hose through the bottom of the dishwasher and attach it to the 90-degree inlet with the proper compression fitting.
Connect the electric circuit to the dishwasher. Pull the electric cable through the bottom of the machine as you did with the water supply in Step 6 above. Connect the proper wires (black -> black, white -> white, ground -> ground) and secure them with a wire nut. Cover any exposed wires with electrical tape.
Connect the end of the water supply hose to either the kitchen sink trap or garbage disposal, depending on your kitchen setup. Ensure that the middle part of the hose is higher up than both the drain outlet on the washer and the drain hose termination point. Use a support bracket to hold the middle part of the hose in place.
Turn on the water and electricity to the dishwasher circuit.
Run a test wash with an empty dishwasher. Pay close attention to the water supply and drain hose for leaks. Tighten any fittings, if necessary.
Secure the washer in place with the support brackets. Replace the bottom cover.Source: ehow.com