Comparing Drop-In, Undermount and Vessel Sinks

Bathroom sink bowls come three primary styles: drop-in, undermount and vessel styles. These sinks are meant to be used with a separate countertop and the differences are mostly in the way they attach to the top. All of these sinks can be made from all the popular materials, such as ceramic, metal and acrylic.

Drop-in sinks, sometimes called "self-rimming", are meant to be dropped into a pre-cut hole in the countertop. The rim is larger than the hole. When they are dropped into the hole the rim sits on top of counter. The underside of the rim is perfectly flat to mate to the countertop. To prevent leaks, your installer should put a bead of chalking under the rim. These sinks usually have brackets on the bottom side of the sink to pull the rim tight to the countertop. This is a good type of sink to use with plastic laminate, like Formica, or wood as the finished edge of the countertop will not withstand prolonged exposure to water. The rim will stand higher than the surrounding countertop, so water cannot flow or be swept directly into the sink. The border where the sink and countertop meet are prone to accumulating dirt.
Undermount sinks are attached to the underside of the countertop. A flange running around the outside of the sink, similar to the rim on drop-ins, is flat on it's top to mount tightly against the bottom side of the countertop. The sink is usually held in place with brackets attached to the underside of the countertop and clipped to the sink flange. Your installer should add a bead of chalking to the top of the flange to prevent leaking. The hole in the countertop is usually slightly smaller than the inside of the sink to hide the seam where the two meet. This type of sink is ideal for use with materials that can have a finished edge that resists water, such as stone and solid surface materials like quartz and Corian. While there is a seam, it is usually somewhat hidden below the lip of the countertop and there is no exposed seam to collect dirt.
Vessel sinks sit directly on top of the countertop, like a soup bowl. The inside and outside of the sink are completely exposed. The is sink usually held in place primarily by the drain and it's tailpiece. For comfortable use, the countertop should be somewhat lower than usual, so the rim of the vessel sink is not too high, making use by shorter folks and children awkward. While stylish, they do present coordinaton problems when picking faucets and drains.
Integrated sinktops combine the sink and countertop into one piece. These are usually some ceramic material such as vitreous china or cast polyester. These sinks offer a seamless design in a single color throughout the sinktop. The seamless design enhances cleanliness. Odd or larges sizes are generally not available. Strasser offers a group of these sinktops.
Other types of sinks, not for use with countertops, include pedestals, consoles and wall mount sinks.