What to do about cracks in a kitchen sink

Q: We had a Corian countertop and a dual Corian sink installed about 20 years ago. The sink has developed shallow fractures around the drains. Is there a way to refresh the sink surface, perhaps by sanding? If so, can I hire a professional to do it?

Columbia, Md.

A: Sink materials include porcelain enamel on cast iron (the sink your grandmother might have had — in white, of course), enameled steel, solid metal (stainless steel or copper), fireclay, natural stone (such as limestone) and manufactured materials that incorporate plastic resins with powdered stone or other minerals. Corian, a DuPont product that's about ⅓ acrylic resin and ⅔ minerals, is in that final category.

Of all the options, stainless steel and copper won't chip or crack. Sinks with a coating, whether it's baked-on porcelain enamel or enamel paint, are much more vulnerable to this kind of damage. But with a small container of color-matched paint and a tiny paintbrush, you can cover chips and make them less noticeable. These repairs work best on a lip or other part of the sink that isn't frequently immersed in water; around a drain, touching up the finish might not be enough to keep rust from forming where the finish cracked or broke off.

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Fireclay, which is a ceramic material made by mixing clay and glaze, can crack or chip if you drop something heavy on it, but it takes more force to do damage. A customer-care representative who specializes in answering technical questions about sinks at Elkay, a sink manufacturer, said fireclay and composite granite sinks sometimes develop hairline cracks around a drain when a high-power garbage disposal is overtightened.

Hairline cracks, such as the ones you’re seeing, can also develop because of rapid changes in temperature. Elkay advises running cold water while pouring boiling water into the sink, such as when you’re draining pasta; Corian offers a similar warning. Adding the cold water helps spread out the area being heated by the boiling water, which reduces the chance that the sink might crack, the Elkay representative said.

It is possible to repair cracks in countertops made of composite materials such as Corian, and it's possible to fill a chip in a sink or a countertop with a two-part epoxy or an acrylic-based patch material. But for cracks in the base of the sink, like you have, there are really only two options: Replace the sink, or live with the cracks, which, fortunately, are a cosmetic issue, not a structural one.

Holly Klee of SurfaceLink, the company that responds to warranty calls from Corian, said patching hairline cracks in a Corian sink doesn't work long-term and can even result in a sink that leaks. "What causes cracks to happen is going from hot water to cold too fast," she said. "If you repair them, they could reopen." Corian sinks are only about a half-inch thick, Klee said, so if the new cracks are deeper, the sink could begin to leak, which would lead to a mess and maybe even cabinet and floor damage.

Corian sinks are typically glued to the underside of a Corian countertop, creating a seamless, easy-to-clean transition. It might seem as if you’d need to replace the countertop to get a new sink. Usually, though, it's possible to have a countertop repair company use a router to cut out the sink, so a new one can be installed, said both Klee and Winkhel Sahagun, owner of the Countertop Guru in Sterling, Va. (703-430-0007; gurutops.com).

Whether you could install a new Corian sink or would need to switch to a different type of material would depend partly on whether the opening fits the dimensions of a sink that's available. Klee said it's "about 50-50" whether an individual homeowner has a model that Corian still makes.

And there are other issues to consider, too. "We can remove the sink. We can remove the glue that's left," Sahagun said. "That's not a problem, in most cases, but we have to figure out whether we can get a new sink inside the cabinet." When there isn't enough unencumbered space underneath to maneuver a new sink into place, it's sometimes possible to remove the countertop and take it outside. The new sink can be installed there before the whole assembly is hauled back inside.

But some countertops are too big or awkward to move. In that case, you’d need to switch to a sink made of a different material. It might need to be a drop-in style, with a lip that would cover a slight mismatch between the opening on the countertop and the shape of the sink. A company that installs and repairs Corian countertops can help assess your options.

Sahagun said replacing a single-bowl Corian sink with a new one in an existing kitchen countertop usually costs $800 to $1,000, including demolition, the new sink and labor other than plumbing work. For a double-bowl sink, it's about $1,000 to $1,600. A bathroom sink might run about $500.

Since Nov. 1, 2004, DuPont has offered a residential 10-year warranty on Corian countertops and the sinks it makes. Your sink is too old to qualify, but if it were newer, you might wonder how the fine print on the warranty affects sinks with cracks like the ones you’re seeing. It specifically excludes "damage from excessive heat," which it defines as "exposure to heat of such a degree that white marks, white rings or cracks appear on the product." This language might seem to give DuPont room to wiggle out of dealing with cracked sinks installed less than 10 years ago, but Klee said that DuPont does regularly pay to replace these sinks as part of its warranty protection. The reason, she said, is that there is often no way to prove that rapid temperature change caused the cracks. "Cracking around a drain is not provable," she said. "We don't know 100 percent, so we put it as ‘unknown cause.’ "

In situations where the cause can be pinpointed, though, the exclusion would apply. The "Use & Care" section of the Corian website warns against allowing water from an instant-boiling-water tap to flow into a Corian sink: "A container should be used to collect boiling water at all times as boiling water from this type of tap may cause surface damage in and around the Corian Solid Surface sink. This type of damage is not covered by the DuPont 10 Year Warranty."

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