Nobody sells a sink with water filter built into the basin. What people mean is a faucet that delivers filtered water, fed by a cartridge or membrane hidden in the cabinet below. Understanding it as a faucet and plumbing job rather than a sink purchase changes what you shop for and what you ask an installer.
Counter holes decide your faucet options
Kitchen counters are drilled with a fixed number of holes, typically one to four, and a dedicated filtered water faucet needs one of them. If your sink deck is fully occupied by the mixer, a sprayer and a soap dispenser, something has to give: sacrifice the soap dispenser, use a combination faucet that delivers both filtered and unfiltered water through separate internal passages, or have a new hole drilled, which is straightforward in stainless steel and risky in stone or solid surface.
What goes in the cabinet, and how much room it needs
A plain carbon filter is a housing about the size of a large thermos with a bracket on the cabinet wall, plus enough clearance below to unscrew the sump. A reverse osmosis unit adds a storage tank roughly the size of a small propane cylinder, which is the part that surprises people, along with the membrane housing and prefilters. Measure before you buy, remembering that the waste bin, the disposal and the trap are already competing for the same space.
The drain and the supply connections
A carbon filter taps the cold supply with a compression tee or a proper shutoff and needs nothing else. Reverse osmosis additionally needs a drain connection, normally a saddle clamped to the sink tailpiece above the trap, and many jurisdictions require an air gap faucet or an approved alternative so drain water can never siphon back into the unit. Check the local plumbing code before choosing a faucet, because the air gap requirement determines which faucets are acceptable.
Living with it after the install
The maintenance is a cartridge change on a schedule, which is easy if you left yourself clearance and miserable if you did not. Fit isolation valves so you can change a filter without shutting off the house, label the install date on the housing, and keep the spare cartridge where you will see it. If the water problem you are solving also shows up in the shower or on the laundry, treat this as the drinking water half of a bigger fix and look at whole house options in parallel.
Questions people ask about sink with water filter
Can I add a filtered faucet to an existing sink?
Usually yes. If there is a spare hole or an unused sprayer hole you can use it directly, otherwise a stainless steel deck can be drilled and stone counters should be drilled by a fabricator.
Is a combination faucet worth it?
It saves a hole and looks tidier, keeping filtered and unfiltered water in separate internal passages. The trade off is that replacing it later means replacing the main faucet, not just the filter tap.
Do I need an air gap faucet for reverse osmosis?
Many local codes require one so drain water cannot siphon back into the system. Check with your local building department before buying the faucet, since it changes the model you need.