Reattach an Undermount Kitchen Sink


An undermount kitchen sink can provide a seamless and stylish look in your kitchen. However, these sinks attach to the underside of the countertop, which means they can be tricky to remove and reinstall if needed. Fortunately, with care and patience, reattaching an undermount sink is a manageable DIY project for most homeowners.

In this comprehensive guide, we’ll walk through the entire process of detaching and reattaching an undermount sink step-by-step. We’ll cover:

  • Reasons why you may need to remove and reattach an undermount sink
  • Preparing for the project, including supplies needed
  • Safely detaching the sink from the countertop
  • Thoroughly cleaning the sink and countertop surfaces
  • Reapplying silicone caulk and reinstalling the sink
  • Ensuring a watertight seal between sink and countertop
  • Tips for preventing leaks and other problems

By the end of this guide, you’ll have the knowledge and instruction needed to successfully reattach an undermount kitchen sink on your own. So let’s get started!

When Do You Need to Reattach an Undermount Sink?

There are a few situations that may require detaching and reinstalling an undermount kitchen sink:

  • Replacing the countertop: If you’re replacing the countertop material, such as swapping out laminate for granite, the existing undermount sink will need to be removed and then reattached to the new countertop.
  • Deep cleaning: Over time, dirt, grime, and calcium deposits can build up around the rim and edges of an undermount sink. Detaching it provides better access for a thorough deep cleaning.
  • Fixing leaks: If the caulk seal around the sink perimeter has dried out or cracked, it can lead to water leaks. Reattaching the sink provides an opportunity to remove old caulk and re-seal for a watertight connection.
  • Repairing damage: Things like cracks in the sink or corrosion around the drain require removing the sink to make full repairs. Reattachment is needed after repairs are made.
  • Changing design: Some homeowners opt to remove an existing undermount sink as part of a kitchen remodel, in order to install an updated or more preferred sink model.

No matter the reason, the process for properly detaching and reattaching an undermount sink is a straightforward DIY project, as we’ll discuss next.

Preparing for the Project

Taking time to prepare appropriately will make detaching and reinstalling your undermount sink much smoother. Here’s an overview of what you’ll need:


  • Safety gloves, glasses, and mask
  • Flat pry bar
  • Putty knife
  • Silicone caulk (clear or color-matched to countertop)
  • Rags
  • Denatured alcohol
  • Utility knife
  • Plumber’s putty
  • Fasteners (screws, bolts, etc.) if reusing existing hardware


  • Cordless drill
  • Phillips and slotted screwdrivers
  • Basin wrench
  • Sandpaper or emery board
  • Jigsaw (if sink openings needs modification)

Other Preparations

  • Clear out under-sink cabinet to allow room to work
  • Turn off water supply lines and disconnect drain connections
  • Remove sink strainers and garbage disposal if applicable
  • Have a helper on hand for detachment and reattachment

Take your time gathering necessary supplies and tools. Ensuring you have what’s needed before starting will prevent delays and frustration.

How to Detach an Undermount Sink

With preparations complete, it’s time to detach the undermount sink. This is the most physically demanding part of the project, so go slowly and take care.

  1. Remove caulk: Use a utility knife to carefully cut away existing caulk around the entire sink perimeter. Go slowly to avoid gouging the countertop surface.
  2. Loosen fasteners: If your sink was originally secured with metal clips, screws, or bolts, locate these fasteners around the underside rim. Use a screwdriver or drill to begin loosening the hardware.
  3. Break seal with pry bar: With fasteners loosened, work a pry bar around the sink rim, gently prying upwards to break the seal. Apply pressure evenly to avoid cracking the countertop.
  4. Lift sink out: Once fully detached, lift the sink out of the countertop opening. This may take some effort if caulk residue remains. Set sink aside safely supported on a folded towel.
  5. Remove leftover caulk: Use a putty knife and rags with denatured alcohol to clean away any remaining caulk from the rim of the countertop sink opening.
  6. Modify opening if needed: If installing a new sink, use a jigsaw to enlarge the countertop opening as required. Sand edges smooth.

With the sink fully detached, the countertop and sink surfaces can now be thoroughly cleaned before reattachment.

Cleaning Surfaces for Reattachment

Proper cleaning of the sink and countertop surfaces is crucial for establishing a watertight seal when reattaching the sink. Here are the steps:

  1. Clean sink: Wash entire sink surface with soapy water, then rinse and dry. Use denatured alcohol to remove any oily residue.
  2. Sand sink rim: Lightly sand the outer rim of the sink that will contact the countertop. This promotes better caulk adhesion.
  3. Clean countertop: Use denatured alcohol and rags to thoroughly clean the sink rim on the countertop underside. Remove all old caulk residue.
  4. Sand countertop: Lightly sand the underside sink rim area to roughen the surface for improved caulk bonding.
  5. Remove dust and debris: Carefully wipe away all dust and debris from the sanded areas on both sink and countertop, using a dry rag or vacuum crevice tool.
  6. Dry all surfaces: It’s critical that both mating surfaces are completely clean and dry for reattachment. Allow sufficient time for denatured alcohol to fully evaporate.

After cleaning, inspect both sink and countertop surfaces for any remaining debris or moisture. Proper cleaning is vital for a leak-proof seal with the fresh caulk.

Reapplying Silicone Caulk

With surfaces prepped, it’s time to apply a fresh bead of silicone caulk around the countertop sink opening. Follow these steps:

  1. Load caulk gun: Cut tip of caulk tube at 45° angle. Load caulk gun, placing tube end into barrel at opening.
  2. Apply caulk: Run a steady bead of caulk around the sink opening rim on the countertop underside. Keep caulk bead uniform for proper adhesion.
  3. Smooth caulk: Before reattaching sink, use a damp finger to smooth out the caulk bead and remove any gaps or air bubbles.
  4. Allow drying time: Let caulk dry and become tacky per manufacturer instructions, usually 20-30 minutes. This helps it stick to sink rim.
  5. Add plumber’s putty: For additional leak protection, roll plumber’s putty into rope shapes. Press into sink drain and faucet holes.
  6. Attach drain hardware: Reattach drain baskets, flanges, and tailpieces to sink underside if previously removed. This prevents losing pieces during reattachment.

Take care to apply fresh caulk properly, as this seals the sink to the countertop and prevents water leaks. Don’t skimp on caulk – a thicker bead is better. Now the sink can be reinstalled.

Reinstalling the Undermount Sink

With fresh caulk applied and ready, it’s time to reinstall the undermount sink to the countertop. Here are the steps:

  1. Lift sink in place: Have a helper hold the sink up to the countertop opening. Ensure sink rim aligns evenly all around.
  2. Apply pressure: While helper holds sink in place, press upwards firmly and evenly on sink bottom to adhere it to caulk. Continue applying pressure for 1-2 minutes.
  3. Reattach hardware: If reusing original metal fasteners, drill pilot holes as needed and reinsert screws, clips, or bolts around rim and tighten down.
  4. Check seal: Visually inspect caulk bead around entire sink perimeter from below to ensure no gaps. Reapply caulk if needed.
  5. Make drain and supply connections: Reattach drain tailpiece, trap, and p-trap. Reconnect supply lines to faucet and valves. Check for leaks.
  6. Seal with caulk: Run a final bead of caulk around the sink rim for an extra-secure seal. Smooth with fingertip and allow drying completely.

Take your time ensuring the sink gets evenly and securely reattached. Having a second pair of hands is very helpful here. With the sink fully reinstalled, cleanup and testing remain.

Finishing Touches

Once your undermount sink is reattached properly, finish up with these steps:

  • Wipe away any excess caulk smears using a rag with denatured alcohol
  • Reinstall sink strainers, pop-up stoppers, garbage disposal if previously removed
  • Turn on water supply valves and check for leaks underneath
  • Run water into sink basins and check for leaks around drain seals
  • Make any minor caulk repairs needed to fix leaks
  • Allow caulk to cure fully for at least 24 hours before using sink
  • Properly dispose of all tools, rags, and debris

Be sure to take a few minutes addressing these finishing touches. Thoroughly cleaning up provides a nice finish to your sink reattachment project.

Tips for Preventing Leaks

To get the longest leak-free service from your newly reattached undermount sink, keep these tips in mind:

  • Always use high-quality silicone caulk designed for kitchens and baths
  • Apply caulk in thick, consistent beads without gaps
  • Ensure caulk sticks to clean and dry surfaces
  • Smooth caulk with fingertip before reattaching sink
  • Allow caulk to fully cure before running water in sink
  • Avoid overtightening faucet and drain connections
  • Seal penetrations at supply line holes, overflows, etc.
  • Periodically check caulk for deterioration and reapply if needed
  • Use a towel or silicone mat under the sink rim to absorb errant drips

Common Questions about Reattaching Undermount Sinks

What’s the best way to detach an undermount sink that’s caulked on?

  • Use a utility knife to cut through the caulk seal around the sink’s perimeter. Then work a pry bar around the rim, gently prying upwards little by little until the sink releases from the countertop. Loosening the sink evenly prevents cracking the countertop.

Do I need to buy a new undermount sink bracket kit for reinstallation?

  • Usually not, unless your original brackets are badly rusted or damaged. In most cases, you can reuse the existing sink clips, screws, or bolts. Just be sure to thoroughly clean the hardware before reinstalling.

What should I do if my jigsaw cuts aren’t perfect modifying the sink opening?

  • Minor imperfections are fine, as long as the sink rim still rests flush to the countertop. Use sandpaper to carefully smooth any significant jagged edges so they don’t interfere with the caulk seal.

How long does it take for silicone caulk to fully cure?

  • Complete curing takes 24-48 hours. Avoid running water or applying heavy pressure to the sink during this time. The caulk will be solidified enough in 2-4 hours to check for leaks.

Why does my newly caulked sink have a slight odor?

  • That’s normal off-gassing from the caulk as it cures. Ventilate the area, and the odor will dissipate within a few days. It’s non-toxic and doesn’t affect the caulk bond.

Reattaching an undermount sink is a very doable DIY project, even for novices. Just work slowly, use quality caulk, and remember the tips above. Relax and enjoy your revitalized kitchen sink!


Detaching and reinstalling an undermount kitchen sink is a straightforward project that most homeowners can accomplish themselves. By following the steps outlined here for proper detachment, cleaning, caulk application, reattachment, and leak prevention, you can avoid the hassle and cost of calling in a plumber.

While careful effort is required, the ability to reattach an undermount sink gives you flexibility in maintaining and updating your kitchen. Hopefully this guide has provided all the instruction needed to complete this useful DIY home improvement project. So gather your supplies, take your time, and soon you’ll be reattaching your undermount sink like a pro.