Replacing a dishwasher is fairly simple. Most units fit neatly into a 24-inch-wide undercounter cavity, and all are prewired and ready for simple supply, drainage, and electrical hookups. Installing a new dishwasher, however, is a much larger job: You must make room for it and bring in electrical, supply, and drain lines. To avoid straining the discharge pump, position the dishwasher as near to the sink as possible.
To get the most from your dishwasher after it's installed, learn about hard water residue in your dishwasher, reasons dishes aren't dry and finding the best dishwasher detergent for your dishwasher>.
Time: About two hours to replace a dishwasher; a full day or more to put in a new one.
Skills: Simple electrical and plumbing skills for replacing; carpentry and basic plumbing and electrical skills for a new installation.
Tool Tip: Electrical tools and carpentry tools will also be needed for this project.
Step-by-Step
1. Prepare the opening
NOTE: Shut off the water, and shut off the electrical power. If you are replacing an existing dishwasher, remove its lower panel and disconnect the supply line, the drain hose, and the electrical line. Remove any screws attaching it to the countertop, and carefully pull the unit out.
For a new installation, remove a 24-inch-wide base cabinet, or tailor a space to fit the dishwasher. Bore a hole large enough to allow for the supply and drain lines near the lower back of the side panel of the adjoining cabinet. The dishwasher will need its own 15- or 20-amp circuit. Run a circuit from the service panel (you may want to hire a licensed electrician to install this).
2. Run the supply line
Cut into the hot water supply line, and insert a standard tee fitting, a nipple, and a shutoff valve. Run flexible copper tubing into the cavity, leaving enough line to reach the dishwasher supply fitting.
3. Provide a drain fitting
Your dishwasher can drain either into the sink drain or into a garbage disposal if you have one. For sink drainage, install a dishwasher tailpiece. Loosen the slip nuts and remove the tailpiece, insert the dishwasher tailpiece into the trap, and cut the old tailpiece to fit above it. Connect all the pieces, and tighten the slip nuts.
To drain a dishwasher into a garbage disposal, use a screwdriver and hammer to remove the metal knockout inside the dishwasher drain nipple located near the top of the disposal. The knockout, when freed, may fall into the grinding chamber of the disposal, so be sure to take it out.
4. Attach the drain line
Thread the drain line through the hole in the cabinet, and slip it onto the dishwasher tailpiece or drain nipple--you may have to push hard. Secure it with an automotive hose clamp.
To ensure proper operation of the appliance, the drain line must make a loop as shown at top right, so that at some point it is raised near the height of the countertop. Support the drain line securely — it will vibrate during use — by wrapping a couple of lengths of wire around it and fastening them to screws driven into the underside of the countertop. Take care that the screws do not poke through the countertop.
Some local codes require an air gap (see inset) at the top of the loop. You can place this in a knockout hole in the sink, or drill a hole for it in the countertop. Run one line from the drain nipple to the air gap, another from the air gap to the dishwasher drain outlet.
5. Make the hookups
Position the ends of the three lines approximately at the locations where they will be connected to the dishwasher. Remove the bottom cover plate from the dishwasher, and slide the unit carefully into place, watching to make sure no lines are damaged. Make sure the dishwasher is all the way in position.
Make the connections as shown in the detail drawings. Tighten the compression nut and drain line clamp firmly, and make secure electrical connections.
Level the dishwasher by turning the leveling screws on the legs. Anchor the dishwasher to the underside of the countertop with screws. Turn on the water and the electrical power. Before reattaching access panels, run the washer, watching carefully for leaks.
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