diagram explaining dishwasher installation
Illustration Gregory Nemec


Energy-efficient and water-saving dishwashers may have the most up-to-date technology, but thankfully they have the same three basic connections dishwashers have been using for decades: a water supply, a drain line, and an electrical hookup. That means if you're replacing a dishwasher, you only need to break these connections from the old appliance and reattach them to the new one. (Shut off power at the breaker panel and close the hot-water valve under the sink first, and be sure to unscrew the old unit from the underside of the counter before pulling it out.)

The existing electrical wiring is still good, but both plumbing lines should be replaced. Dishwashers come with drain hoses, but you'll need to buy a supply pipe—preferably copper tubing, which TOH plumbing and heating expert Richard Trethewey uses instead of braided steel. "Copper is time-proven," says Richard. "Inside a braided line is rubber, which can eventually fail. Copper lasts 60 to 80 years—longer than any dishwasher."

Though traditionally dishwashers get hooked up to the hot-water supply, you can save even more energy by connecting to the cold water because the heating element in the dishwasher uses less power than a water heater. However, check manufacturers' literature—some companies' models must be supplied with hot water.

The most difficult part of the installation may be snaking the copper tubing through the cabinet without kinking it. An invaluable tool for this is a tube-bending spring, which fits either inside the pipe or around it and bends it with even pressure. But Richard points out that it's the easiest of the connections—the drain line—that actually causes the most trouble. It must be installed strapped up high in an upside-down U to prevent sink backflow from going into the dishwasher. Also, if you're installing a model that sits flush with the front of the cabinets, you may have to drill new, lower holes from the dishwasher bay to the supply valve so the plumbing lines snake along a narrow inset at the back of the unit, allowing you to push it all the way to the wall.

Luckily, the electrical connection is fairly straightforward; just make sure to clamp the wires - be they metal-sheathed BX cable or vinyl-wrapped Romex - to the unit's junction box. This protects against electrocution should there be any leaks.
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    Tools List

    • flathead screwdriver
    • drill
      fitted with 1 1/4-inch and 2-inch hole saws
    • spade bit
      1-inch spade bit
    • needlenose pliers
    • adjustable wrench
      Adjustable wrench
    • Tube Bending Springs
      Tube Bending Springs
    • close quarter tubing cutter
      Close-quarter tubing cutter
    • torpedo level
      Torpedo level
    • wire strippers
      Wire Strippers

    Shopping List

    The majority of built-in dishwashers come in only two sizes: 24 inches wide and 18 inches wide, both sized to fit under a standard 25-inch-deep and 36-inch-high counter. (Be sure to get a built-in dishwasher, not a portable one, which uses temporary connections at a sink tap and outlet.) Look for the Energy Star label on any model you buy—the criteria for dishwashers became more stringent in January 2007.

    2. 3/8-TO-½-INCH BRASS ELBOW
    to make the turn from the dishwasher's inlet to the copper supply line. This is a standard part for dishwashers and may be included in a dishwasher installation kit.


    to bring water to the dishwasher. (The measurement refers to the pipe's outside diameter.) A 10-foot coil should be plenty.

    The number also refers to outside diameter. Each includes a brass ferrule (or compression sleeve) and a compression nut.

    6. ELECTRICAL WIRE NUTS to connect wire ends.
    Get ones that will fit two 12-gauge wires—either yellow or red.

    to secure the electrical cable to the junction box on the dishwasher.

    8. NO. 6 HOSE CLAMP
    to attach the dishwasher's 5⁄8-inch drain hose to the sink's drain tailpiece.

    to hang the drain hose on the cabinet wall.