Replace an Undermount Sink Clip

Undermount sink clips are the unsung workhorses of kitchen plumbing. These small metal brackets grip the sink rim and hold several hundred pounds of porcelain, water, and dishes against the underside of your countertop. When one fails—usually from corrosion or over-tightening during installation—the sink can shift, leak, or in rare cases, detach entirely. Replacing a failed clip takes thirty minutes and requires working in the awkward space beneath your sink. The work itself is straightforward, but the confined quarters and the need to support the sink while you work make this a two-person job if the sink is fully installed. Most clips are universal fit, but matching the original style ensures proper load distribution across all mounting points.

1. Locate and photograph the clip. Remove everything from the cabinet beneath the sink. Use a flashlight to locate the failed clip and examine how it attaches—most clips have a threaded post that screws into an insert embedded in the countertop underside, with a cam or bracket that rotates to grip the sink rim. Note the clip style and position before removal.
2. Brace the sink weight. If other clips are still holding, you can work without additional support. If you're replacing the last functioning clip or the sink feels loose, place a length of 2x4 or an adjustable jack post from the cabinet floor to the sink bottom. Apply just enough pressure to take the load off the clips without lifting the sink away from the countertop.
3. Extract the old clip. Turn the clip cam or bracket away from the sink rim to release tension. Unscrew the threaded post counterclockwise—it threads into a metal or plastic insert in the stone. If the post spins without unscrewing, the insert has failed and you'll need to drill a new mounting hole two inches away from the old one.
4. Clear debris and corrosion. Wipe away any dried silicone, mineral deposits, or corrosion from the sink rim and countertop underside where the clip makes contact. The clip bracket must sit flush against clean material to distribute load properly. If the old mounting insert pulled out, clean the hole and verify the new insert will bite into fresh material.
5. Mount the new insert. If the original insert failed, drill a new hole using a carbide-tipped bit sized for your insert—typically 3/8 inch for granite or 5/16 inch for wood substrates. Tap the threaded insert into the hole with a rubber mallet until it sits flush. Some inserts require a setting tool that threads into the insert and pulls it tight as you turn.
6. Thread and position the clip. Thread the new clip post into the insert until it's finger-tight. Rotate the cam or bracket so it clears the sink rim, then position the clip assembly so the bracket will grip the rim evenly when rotated into place. Thread the post in two more full turns, then rotate the bracket to engage the sink rim.
7. Snug the bracket firmly. Use a wrench or socket to tighten the clip post while holding the bracket in position against the sink rim. Tighten until the bracket pulls the sink firmly to the countertop underside—you'll feel resistance increase noticeably. Stop when the sink rim compresses slightly against the countertop. Check that the sink hasn't shifted by measuring the reveal around the drain opening.
8. Verify the hold under load. Remove any temporary support from beneath the sink. Fill the sink with six inches of water and inspect all clip locations for movement or gaps opening between sink and countertop. Let the water sit for five minutes, then drain while watching the clip—it should hold position without flexing. If the sink drops or shifts, the clip needs another quarter turn of tightening.