The Best Ways to Repair a Cracked Sink

It happens: You’re washing your hands or the dishes and you notice a crack in your sink. It’s tiny, and a quick check assures you that your sink isn’t leaking—but it is the nature of cracks to get worse over time, and even if a hairline crack in your sink isn’t particularly noticeable, they can blacken and discolor over time, or (depending on the type of sink you have) cause the underlying metal to rust.

Sinks crack for one of three reasons: You dropped something heavy on it; you have an over-tightened drain connection or garbage disposal; or you inflicted what’s known as “thermal shock” on your poor, suffering sink either by running extremely hot water into it or switching suddenly from cold to very hot water. Porcelain and other materials commonly used in sinks react to those temperature swings by contracting and expanding, and if that happens too fast you get a crack.

The good news is that if your sink isn’t leaking you can repair the sink instead of replacing it. If you take your time and work carefully, the repair can be almost unnoticeable.

Know what your sink is made of

While the basic process of fixing a crack in your sink is more or less the same, you need to match the repair material with your sink. The most common choices—aside from solid metal like stainless steel or copper—are:

Porcelain enamel on metal or fireclay
Natural stone
Fiberglass
Solid surface materials (e.g., Corian)

Once you know what you’re trying to repair, you can proceed with the repair.

The best way to repair your sink

The best way to repair a cracked sink is to fill in the crack with a waterproof bonding material, then sand and paint the repair to match the rest of the sink. Done properly, this will not only hide the imperfection, it will prevent moisture from causing damage to the sink. First, buy some repair material:

For solid-surface sinks, check with the manufacturer to see if they offer or recommend a specific repair kit. Otherwise, a waterproof epoxy like J-B WaterWeld will work well.
For natural stone, a seam filler designed specifically for stone will work.
Any fiberglass repair kit will work for a fiberglass sink.
For a porcelain surface sink, a porcelain filler will do the job.

While you should follow the specific instructions that come with each of these products, they all follow the same basic steps:

Clean thoroughly. Like, really clean that sink. Focus on the cracked area and use a degreaser to make sure you get all the grime and junk out of there.
Sand the area with a very fine (400 grit) sandpaper, then sand again using rougher (240, then 120 grit) sandpapers. Concentrate just on the immediate area of the crack. If your crack is in a seam and hard to reach, try gluing some sandpaper to the edge of a paint stirrer.
Clean again, using a vacuum to suck up the fine dust from your sanding.
Mix and apply your repair agent according to the instructions. Use just enough to fill in the crack. Depending on the material, you can use a small artist’s paintbrush or even a toothpick to work it into the space of the crack.
Let it dry according to the instructions, then sand lightly so it’s flush.
Apply a second layer of material if the crack is still visible, then let dry and sand lightly again. Repeat as necessary, sanding each time.
Paint your repair with a touch-up paint if the repair kit did not provide a finish. You can find these in different colors.

Once the paint dries, your repair is done and (hopefully) unnoticeable.

The second-best way to repair your sink

If your crack is pretty thin and small, you might be able to repair it using silicone caulk. This is a lot easier, a lot faster, and a lot cheaper, but won’t produce the best aesthetic results—unless you’re very, very careful and a little lucky. Caulk will work best on tiny cracks at the seam of your sink (i.e. where the vertical and horizontal planes meet).

First, isolate the crack with some painter’s tape. Get as close as you can, minimizing the amount of sink surface affected. Try to color-match your sink if possible; a white porcelain sink might match up well with a white caulk, but chances are a perfect match will be difficult. Using the narrowest possible bead, apply your caulk, carefully smooth it into the crack, then remove the tape and let it dry. This will at least hide the crack and stop moisture from infiltrating, and with a little luck won’t look too bad.

A tiny crack in your sink isn’t a huge problem. With just a few hours of your time and a small amount of money, you can repair it before it becomes one.