The first and most critical step is to ensure the work area is safe. Go to your home's main electrical panel and turn off the circuit breaker that powers the dishwasher. Then, locate the hot water shutoff valve under the kitchen sink, which supplies the dishwasher, and turn it fully to the 'off' position. Lay down several old towels in front of the dishwasher and under the sink to absorb any residual water that will spill during disconnection.

Under the sink, place a small bucket to catch water from the hoses. First, disconnect the drain hose, which is typically connected to a nipple on the garbage disposal or a wye-tailpiece on the sink drain. Use a flathead screwdriver or nut driver to loosen the hose clamp, then pull the hose off the nipple. Next, disconnect the water supply line. Use an adjustable wrench to loosen the compression nut connecting the supply line to the hot water shutoff valve. Have towels ready as water will drain from the line. Finally, disconnect the other end of the supply line from the dishwasher's inlet valve, which is usually at the front, behind a lower access panel.

After all lines (plumbing and electrical) are disconnected, the old unit can be removed. Open the dishwasher door and look for two mounting brackets that secure the top of the dishwasher to the underside of the countertop. Use a screwdriver to remove these screws. With the screws removed, you can now carefully slide the old dishwasher straight out of the cabinet opening. You may need to adjust the front leveling feet downwards (counter-clockwise) to create enough clearance.

Prepare the new dishwasher for installation before sliding it into place. Carefully tip the new unit onto its back on a piece of cardboard to protect it. Locate the water inlet valve. Wrap the male threads of a new 90-degree brass elbow fitting with 3-4 layers of Teflon tape in a clockwise direction. Screw this fitting into the dishwasher's plastic inlet valve, hand-tightening first and then giving it a gentle quarter-turn with a wrench. Do not over-tighten, as this can crack the plastic housing. Orient the elbow to point towards the rear of the dishwasher, where the water line will connect.

Carefully slide the new dishwasher part-way into the cabinet opening. Before pushing it all the way in, feed the drain hose, the new water supply line, and the electrical cable through the access hole in the side of the cabinet into the sink base. Once the lines are through, push the dishwasher the rest of the way in. Use a level on the top edge of the inner door to check for levelness side-to-side and front-to-back. Adjust the dishwasher's feet with an adjustable wrench until it is level and fits snugly beneath the countertop.

Connect the new braided water supply line to the 90-degree elbow you installed on the dishwasher. Hand-tighten the coupling, then give it a final quarter-turn with a wrench. Route the other end to the hot water shutoff valve under the sink. Attach the line to the valve, ensuring the threads are aligned correctly to prevent cross-threading. Tighten the nut with an adjustable wrench until it is snug. If connecting to a copper pipe shutoff, use a second wrench to hold the valve body steady to prevent twisting and breaking the pipe.

Route the new drain hose from the dishwasher to the garbage disposal's inlet nipple. To prevent contaminated water from the sink from flowing back into the clean dishwasher, create a 'high loop' with the hose. Secure the drain hose as high as possible against the underside of the countertop or the back wall of the sink cabinet before it loops down to the disposal nipple. Use a strap or zip tie to hold it in place. Slide the spring clamp or hose clamp over the end of the hose, push the hose firmly onto the nipple, and move the clamp into position to secure it tightly.

With all plumbing connections made, it's time to test for leaks before finishing the installation. Place a dry paper towel under the hot water shutoff valve and where the supply line connects to the dishwasher. Slowly turn the water shutoff valve all the way on. Use a flashlight to carefully inspect both connection points for any signs of dripping. If any moisture appears, turn the water off and tighten the leaking connection slightly. Once you confirm the supply side is dry, turn the power back on at the circuit breaker. Start a 'rinse only' or 'quick wash' cycle. As the dishwasher fills and then drains, check the supply and drain line connections again for any leaks.

After confirming the dishwasher runs without any leaks, perform the final step. Open the dishwasher door and locate the mounting brackets at the top of the unit. Using the provided screws and a screwdriver or drill, fasten these brackets to the underside of the countertop. This secures the dishwasher in place, preventing it from tipping forward when the racks are loaded and pulled out. Finally, install the lower toe-kick panel at the base of the dishwasher, which usually snaps or screws into place.