How to Mount a Dishwasher Under a Quartz Countertop

Installing a dishwasher under a quartz countertop can seem daunting, but with proper planning and the right techniques, it can be done smoothly. Here is a step-by-step guide on how to mount a dishwasher under a quartz countertop.

Choosing the Right Dishwasher

When choosing a dishwasher for under a quartz countertop, opt for a slim, low-profile model. Look for the following features:

  • Height of 32 inches or less to fit under standard countertops
  • Adjustable or removable upper rack to accommodate tall glassware
  • Energy Star certified for efficiency
  • Quiet operation, ideally 40-45 decibels
  • Delay start option to run during off-peak hours
  • Drying fan and heat options for better dry performance

Avoid dishwashers with tall tub designs intended for countertop installations. Compact 18-inch wide models are ideal for small spaces.

Preparing the Underside of the Quartz

Proper preparation of the underside of the quartz countertop is crucial for securing the dishwasher. Follow these steps:

  • Remove any existing backsplash tile or wall coverings in the area the dishwasher will be installed.
  • Check for level and evenness of the underside of the countertop. Use shims if necessary to create a flat mounting surface.
  • Mark the underside of the countertop where the dishwasher will be positioned. Make sure there is proper clearance on all sides.
  • Apply waterproof sealant to the underside around the marked area to prevent moisture damage. Allow sealant to fully cure.

Thorough sealing and checking for levelness will ensure a stable base for mounting the dishwasher.

Creating a Water Supply Connection

The dishwasher will need a hot water supply line. This involves connecting to the hot water plumbing under the sink. Follow these best practices:

  • Shut off water supply and drain lines before starting.
  • Attach a tee connector to the hot water line to split supply.
  • Run a new 1/2 inch copper or braided stainless steel supply line from tee to dishwasher inlet.
  • Use compression fittings for easy install and leak prevention.
  • Keep lines as short as possible with gentle bends to avoid kinks.
  • Turn water back on and check for leaks. Tighten fittings if necessary.

Proper hot water supply line installation prevents leaks and ensures adequate water pressure.

Connecting the Drain Hose

Dishwasher drain hoses usually run through the sink cabinet before connecting to the sink drain pipe. Here are some tips:

  • Remove sink drain p-trap and clean thoroughly before starting.
  • Use hose clamps and tighten all connections.
  • Keep hose short, neat, and gently sloped to prevent backups.
  • Drill a hole in sink cabinet side for cleaner hose routing.
  • Attach high drain loop or air gap kit if required by local codes.
  • Re-install p-trap and test for smooth drainage by running water before mounting dishwasher.

Careful planning of the drain hose route and connections is key to prevent nuisance clogs and backups.

Securing the Dishwasher Under the Counter

Once utilities are connected, you can secure the dishwasher under the quartz countertop. Be sure of the following:

  • Slide dishwasher into place, aligning side brackets with cabinet openings.
  • Confirm dishwasher height is properly aligned with countertop underside.
  • Attach mounting brackets designed for under-counter installation to hold dishwasher snugly in place.
  • Level dishwasher using bracket adjustment screws if needed.
  • Use screws through back of tub to mount tightly to cabinets.
  • Seal any gaps between the tub and cabinet edges with silicone caulk.

Proper mounting and alignment ensures the dishwasher blends seamlessly into the kitchen.

Testing Operation and Finishing Touches

With installation complete, the final steps are:

  • Turn on water and power supply to dishwasher.
  • Open dishwasher and remove packaging materials.
  • Run a test cycle to check for leaks and proper drainage.
  • Adjust racks and controls as needed for smooth door clearance.
  • Add trim kit for a built-in look if desired.
  • Run several cycles using detergent to clean interior before first use.

Taking the time to test and adjust the dishwasher will ensure stress-free performance for years to come.

With attention to detail in preparing the space, making secure connections, mounting the dishwasher properly, and testing operation, you can have a seamlessly integrated dishwasher installed under your beautiful quartz countertop.

Frequently Asked Questions

What type of sealant is best to use under the quartz?

100% silicone sealant is ideal for waterproofing the underside of the quartz around the dishwasher area. Make sure it is specifically formulated for use in kitchen and bath areas.

What should I do if my cabinet opening is slightly wider than the dishwasher?

Use extra long mounting brackets designed for under-counter dishwasher installation. Attach shims along the brackets where they contact the cabinet sides to take up any extra space if needed.

How can I ensure the drain hose runs smoothly to the sink drain?

Use rigid copper tubing or a dishwasher drain hose connector kit to neatly route the hose to the drain pipe. Secure it properly with hose clamps to prevent sagging.

How do I adjust the brackets if the dishwasher is not level?

Consult the installation guide for your specific dishwasher model. Many have leveling feet that can be adjusted from inside the tub using a wrench or screwdriver to raise or lower each corner.

What is the best way to secure the dishwasher in the opening?

Use at least two long screws drilled up from the bottom corners of the dishwasher tub into the cabinet framing. This provides a very sturdy mounting.


Installing a dishwasher under quartz requires careful planning and precise installation techniques. With some patience and attention to detail, it is certainly a doable DIY project. Following the preparation, utility connection, mounting, and testing steps outlined above will result in a durable, seamless installation that matches beautifully with your luxurious quartz countertop. Be sure to thoroughly research your dishwasher model specifications and consult local building codes for compliance. Take it slowly and be meticulous in each phase of the process for best results under your quartz countertop.