How To Replace a Dishwasher

Homeowners who are struggling with faulty dishwashers, or who simply want to upgrade their appliances, should consider replacing their dishwashers themselves. The task may seem daunting, but you can complete it as part of a do-it-yourself project if you properly prepare and learn how to maintain your new system. Read how to replace a dishwasher in our step-by-step guide below, and watch the video above for tips from This Old House plumbing and heating expert Richard Trethewey.

Understanding Dishwasher Replacement

You must take the time to understand the replacement process before you dive in. Replacing a dishwasher typically requires disconnecting the old unit from water, electrical, and drain lines, removing it from its space, and then reversing the process with the new unit. You may need to modify cabinetry or plumbing in certain cases.

When to Replace Your Dishwasher

Here are some signs it might be time for a replacement:

• Repairs are becoming frequent and costly.
• Strange noises occur during operation.
• The dishes aren’t clean after a wash.
• There are visible cracks or damage to the tub.
• Your dishwasher is more than 10 years old.
• Your energy bills have increased significantly.

Older dishwashers are less energy efficient than modern models, and upgrading can reduce long-term utility costs. Today’s dishwashers usually include advanced features that make the machine more efficient and convenient.

In a recent Ask This Old House project, homeowner Jen Wells reported recurring problems with her dishwasher after 13 years of use. After multiple visits from an appliance repair company, Richard Trethewey, the show’s plumbing and heating expert, assessed the situation and concluded: “After 13 years, I don’t think I want to put any more good money after bad. It’s time for a new dishwasher.”

Preparation Steps

Prepare for installation by following the steps below. 

1. Measure your current dishwasher and the cabinet opening to make sure the new unit will fit.
2. Purchase a new dishwasher that matches your measurements and requirements.
3. Gather all necessary tools and materials.
4. Turn off the power to the dishwasher at the main electrical panel.
5. Shut off the water supply to the dishwasher.
6. Protect your kitchen floor with a drop cloth or cardboard to avoid scratches and damage.

Tools and Materials Needed for Dishwasher Replacement

Gather the tools below before you begin the replacement process to make removal and installation much easier.

• 1-inch spade bit
• 1 1/4-inch hole saw bit
• 2-inch hole saw bit
• Adjustable wrench
• Close-quarters tubing cutter
• Drill/driver
• Pliers
• Protective eyewear
• Safety gloves
• Screwdriver
• Shallow pan or bucket
• Teflon tape
• Torpedo level
• Tube bending springs
• Wire stripper

Removing the Old Dishwasher

The first step in replacing your dishwasher is to remove the old unit. Follow the steps below.

Disconnecting Utilities

1. Remove the access panel from the lower front of the dishwasher.
2. Disconnect the electrical wiring by removing the wire nuts and separating the connections.
3. Disconnect the copper water-supply line from the dishwasher. Drain excess water into a shallow pan.
4. Disconnect the drain line by loosening the clamp and pulling it off the dishwasher.

Removing the Dishwasher

1. Open the dishwasher and remove the screws that hold it to the underside of the counter.
2. Carefully slide out the old dishwasher, and be careful not to damage the floor and surrounding cabinetry.
3. Clean up any remaining water in the drain lines. 

Sliding out the dishwasher might require some wiggling. If the unit seems stuck, check for any errant screws or brackets that might be holding it in place.

On one This Old House project, Richard slid a drop cloth under the dishwasher before pulling it out. As he told homeowner Jen: “I don’t want to scratch the floor.” It’s a simple precaution — especially important if you have hardwood or tile — that can save you from costly repairs to your kitchen flooring.

Installing the New Dishwasher

Once you’ve removed the old dishwasher, you can install the new unit. This process involves preparing the space, connecting utilities, and securing the new dishwasher in place.

Preparing the Space

1. Clean the area that hosted the old dishwasher. 
2. Drill a 1-inch hole through the cabinet to feed the soft copper tubing for the water supply.
3. Make sure the electrical and plumbing connections are accessible and in good condition.

Technique Detail: When setting up the water supply, use a drill/driver fitted with a 2-inch hole saw to make the hole through the side of the sink cabinet facing the dishwasher bay, positioning it 3 inches up from the floor and 2 inches in from the back wall. If this hole falls below the cabinet floor, make two 1¼-inch holes at the back of the cabinet floor instead. Carefully uncoil the copper tubing and loosely thread it from the dishwasher bay through the cabinet side and up into the cabinet via one of the floor holes.

Connecting Utilities

1. Feed the soft copper tubing through the hole into the sink cabinet.
2. Use an adjustable wrench to attach the copper tubing to the hot water shut-off valve inside the sink cabinet. Apply Teflon tape to threaded connections to prevent leaks.
3. Disconnect the old drain line from the garbage disposer and attach the new drain hose to the disposer using a stainless-steel hose clamp.
4. Secure the electrical wiring with twist-on wire connectors. Match wire colors for proper connections.

Routing Lines Safely: Before sliding the new dishwasher into the bay, find the two front-to-back clear paths on the underside of the unit — these channels are designed to keep the copper tubing and electrical wiring away from the motor as they run from the back of the dishwasher bay to the front of the appliance. Using an outside bending spring, shape the copper pipe so it wraps down the cabinet side and along the water-pipe channel, then tape both lines to the floor in position over their marked paths so they feed smoothly as you push the unit into place.

Securing the New Dishwasher

1. Tape the hot-water line and electrical cable to the floor to keep them out of the way.
2. Carefully slide the new dishwasher into place, and make sure not to kink or bend any lines.
3. Use a tubing bender to shape the copper line.
4. Cut the tubing to the appropriate length and attach it to the dishwasher using a compression fitting.
5. Secure the electrical wiring with twist-on wire connectors.
6. Connect the new drain hose to the side of the garbage disposer using a stainless-steel hose clamp.
7. Screw the dishwasher to the underside of the countertop to secure it in place.
8. Level the dishwasher using the adjustable feet so that it remains stable and operates quietly.

When leveling, open the dishwasher door and hold a torpedo level against the inside top of the unit, adjusting the front feet until it reads level side to side. Once it’s level and the mounting brackets are flush against the underside of the counter, drive screws through the brackets to fasten the dishwasher in place. Replace the base cover panel, then turn on the power and water supply. Check for leaks at the water connections over the next few hours — if any appear, turn off the water and tighten the compression fittings slightly before test-running the dishwasher.

Troubleshooting Common Dishwasher Issues

You may encounter some issues with your dishwasher even if you install it carefully. Below are some common problems and corresponding solutions:

• Leaks: Check all connections and tighten as necessary. Use plumber’s tape on threaded connections to prevent leaks.
• Noisy operation: Level the dishwasher using the adjustable feet. Make sure you’ve securely mounted the appliance to minimize vibration. 
• Poor drainage: Make sure you’ve properly installed the drain hose with a high loop to prevent backflow. Check for clogs in the drain hose or garbage disposer.

Maintenance Tips for Your New Dishwasher

Follow the maintenance tips below to keep your new dishwasher running smoothly.

• Avoid overloading the dishwasher so the appliance can efficiently clean all the dishes.
• Clean the filter regularly to prevent clogs and maintain water flow.
• Clean the spray arms periodically to remove any clogs that might affect water distribution.
• Inspect the door gasket for signs of wear and replace it if necessary to prevent leaks.
• Run hot water in the sink before starting the dishwasher so that the dishwasher starts its cycle with hot water. This will lead to more successful cleaning. 
• Use rinse aid to improve drying performance and reduce water spots on dishes.

Tools: