What You Need to Know Before You Start
Replacing a dishwasher is a project most home cooks can handle in two to four hours, though the actual difficulty depends on whether your new unit fits the same space and connects to the same plumbing. The core steps are the same: turn off water and power, disconnect the old machine, slide it out, position the new one, and reconnect water, drain, and electrical lines. If your old dishwasher is built-in under the counter, you will need basic hand tools—a wrench, screwdriver, and adjustable pliers—plus a bucket to catch water.
The biggest variable is whether you are replacing an existing dishwasher with a similar model in the same cabinet opening, or installing one where none existed before. This guide covers the replacement scenario. If your new dishwasher is a different width or depth, or if you are installing one for the first time, you may need to modify cabinet openings or add new plumbing connections—work that often requires a plumber.
Key Takeaways
- Turn off the water supply valve under the sink and the circuit breaker for the dishwasher before you disconnect anything.
- The inlet hose connects to hot water, the drain hose runs to the sink drain or garbage disposal, and the power cord plugs into an outlet under the sink or into a hardwired junction box.
- Measure the opening width, depth, and height of your old dishwasher before ordering a new one to avoid installation problems.
- New dishwashers come with an inlet hose and drain adapter, but you may need to reuse your old water supply line if it is not included.
- After installation, run the dishwasher empty on a hot cycle to check for leaks before loading dishes.
Measure Your Space and Check Connections
Before you buy a replacement, measure the opening where your old dishwasher sits. Use a tape measure to check the width (usually 24 inches for standard models), the depth from the front of the cabinet to the back wall, and the height from the floor to the underside of the counter. Write these numbers down. Most dishwashers are 24 inches wide and 24 inches deep, but depths can vary by 2 to 3 inches depending on the model, and that matters when you slide it back into place.
While you have the tape out, look under the sink to see how the old dishwasher connects. You will see three lines: a water inlet hose (usually connected to the hot water supply with a brass fitting), a drain hose (usually a ribbed plastic tube that runs to the sink drain or garbage disposal), and a power cord or hardwired connection. Take a photo of these connections with your phone—it will help you remember where everything goes when you install the new unit.
Turn Off Water and Power
Locate the water supply valve under the sink, usually a small oval or round knob on the hot water line. Turn it clockwise until it stops—do not force it. This shuts off water to the dishwasher inlet hose. If you cannot find the valve or it will not turn, shut off the main water supply to the house instead.
Next, turn off the circuit breaker for the dishwasher. If you do not know which breaker controls it, look at the panel label or turn off the breaker that controls the kitchen outlets. Flip the switch to the off position. If the dishwasher is hardwired (no plug), the breaker is the only power control, and you must turn it off before you touch any electrical connections.
Disconnect and Remove the Old Dishwasher
Open the dishwasher door and look for two or four bolts or screws along the top edge of the frame, usually hidden under the counter overhang. These anchor the unit to the counter. Remove them with a wrench or screwdriver and set them aside—you may need them for the new unit. If there are no bolts, the dishwasher is held in place by friction alone and will slide out once you disconnect the lines.
Slide the dishwasher out partway—about 12 inches—so you can reach the connections underneath. Place a bucket or towel under the inlet hose connection before you loosen it; there will be water in the line. Use an adjustable wrench to turn the brass fitting counterclockwise where the inlet hose meets the water supply. Once it is loose, unscrew it by hand and set the hose aside. If water drips, let it drain into the bucket.
Locate the drain hose where it connects to the sink drain or garbage disposal. If it is clamped with a hose clamp (a metal band with a screw), loosen the screw with a screwdriver and slide the clamp off. Pull the drain hose free. If the hose is glued or sealed, you may need to cut it with a utility knife—the new hose will replace it anyway.
If the dishwasher has a power cord, unplug it from the outlet under the sink. If it is hardwired to a junction box, you will see a metal box with wire connections inside. Turn off the breaker again to be sure, then loosen the wire nuts (the plastic caps holding the wires together) by turning them counterclockwise. Separate the wires and push them back into the junction box. If you are unsure about electrical work, stop here and call a licensed electrician.
Now slide the old dishwasher all the way out and away from the cabinet opening. You may need a helper to tilt it slightly as you pull—dishwashers are heavy and awkward. Set it aside or arrange for pickup.
Position and Level the New Dishwasher
Remove the new dishwasher from its box and inspect it for shipping damage. Check that the inlet hose, drain adapter, and any included hardware are in the box. Slide the new unit into the opening, aligning it with the sides of the cabinet. It should fit snugly but not so tight that you have to force it.
Once the dishwasher is in place, check that it is level using a spirit level on the front edge. If it tilts forward or backward, adjust the front feet by turning them clockwise to raise the unit or counterclockwise to lower it. The unit should tilt slightly backward (about 1/4 inch over 24 inches) so water drains toward the back during the wash cycle. If the feet do not adjust enough, place shims (thin wedges) under the back corners.
Reconnect Water, Drain, and Power
Reconnect the inlet hose first. The new dishwasher comes with a hose, but if it is too short or damaged, you can reuse the old one. Screw the brass fitting onto the hot water supply valve by hand until it is snug, then use an adjustable wrench to tighten it one more half-turn. Do not over-tighten—you only need enough pressure to stop leaks. Turn the water supply valve back on by turning it counterclockwise. Check for drips at the connection; if water leaks, turn the valve off and tighten the fitting another quarter-turn.
Connect the drain hose next. The new dishwasher has a ribbed plastic outlet on the back or bottom. Slide the drain hose onto this outlet and find it with a hose clamp if one is provided. The other end of the hose should run to the sink drain or garbage disposal. If your old hose is still in place, you can reuse it; if not, the new hose is usually long enough to reach. If the hose is too short, you can buy an extension at a hardware store and connect it with a barbed coupling (a plastic fitting that joins two hoses).
Reconnect the power last. If the old dishwasher had a plug, the new one should too—plug it into the outlet under the sink. If the old unit was hardwired, the new one likely is as well. Turn off the breaker again, then connect the wires: black to black, white to white, and bare copper (ground) to green or bare copper. Twist each pair together, screw a wire nut onto each connection, and push the wires back into the junction box. Close the box cover and turn the breaker back on.
find the Unit and Test for Leaks
Slide the dishwasher all the way back into the cabinet opening until the front edge is flush with the cabinet face. If you removed bolts from the old unit, reinstall them through the top frame into the counter to anchor the new dishwasher. Tighten them snugly but do not over-tighten—you only need enough pressure to keep the unit from shifting.
Run the dishwasher empty on a hot cycle to check for leaks. Open the cabinet door under the sink and watch for drips at the water inlet connection and the drain hose. If you see water, turn off the dishwasher and the water supply, then tighten the leaking connection. Once the cycle finishes with no leaks, the installation is complete. You can now load dishes and run the dishwasher normally.
Frequently Asked Questions
Can I install a dishwasher if there was not one before?
Yes, but you will need to add plumbing and electrical connections. This usually requires running a water line from under the sink, adding a drain line to the sink drain or garbage disposal, and installing a dedicated circuit or outlet. This work often requires a plumber and electrician, so it is more involved than replacing an existing unit.
What if the new dishwasher does not fit in the old opening?
If it is too wide, you may need to modify the cabinet opening—a job for a carpenter. If it is too deep, you may need to move the sink or adjust the plumbing. If it is too tall, you may need to remove or adjust the counter. Measure carefully before you buy, and ask the retailer about the exact dimensions of the model you choose.
Do I need to use the hose that comes with the new dishwasher?
The included hose is designed for that model and is usually the safest choice. If it is too short, you can buy an extension or use your old hose if it is in good condition. Do not use a hose that is cracked, kinked, or more than five years old—old hoses can burst and cause water damage.
What if water leaks from the connection after I turn the water back on?
Turn off the water supply valve when ready. Loosen the leaking fitting with a wrench, wrap the threads with plumber's tape (a thin white tape), and screw the fitting back on. Tighten it firmly but do not force it. Turn the water back on and check again. If it still leaks, the fitting may be damaged and you may need to replace the hose.
How long does the whole job take?
Removing the old dishwasher usually takes 30 to 45 minutes. Installing the new one takes another 45 minutes to an hour. If you are comfortable with plumbing and electrical work, the total time is two to two and a half hours. If you need to adjust the cabinet opening or add new connections, add several hours or a day for that work.