How to identify an old faucet cartridge

Start with the brand

Look at the base of the spout, the cap on top of the handle, and the underside of the handle itself. Moen, Delta, Kohler, American Standard and Price Pfister almost always put the name somewhere. A partial name or a logo is enough.

If there's no brand at all, that's a clue too — it often means a builder-grade faucet, and those tend to use a small number of generic cartridges.

Count the handles

Single-handle faucets use one cartridge or ball that controls both temperature and flow. Two-handle faucets use a separate stem or cartridge on each side, and the hot and cold are often different parts — bring both if you can.

Pull it out, carefully

Shut off the supply valves under the sink first. Pop the decorative cap off the handle, back out the set screw underneath, and lift the handle off. Under it you'll find a retaining nut or a small clip holding the cartridge in place. Remove that, and the cartridge pulls straight up. If it's stuck, don't pry with a screwdriver — the body is brass and marks easily. A gentle twist with pliers on the stem usually frees it.

Keep everything you removed, including the clip. Lay it on a paper towel in the order it came out.

What to note

Overall length of the cartridge. Whether the stem is round, D-shaped, or splined — and if splined, roughly how many teeth. Whether it's plastic or brass. Any numbers stamped on it. A phone photo next to a tape measure captures most of this at once.

Then bring it in

Put the old cartridge in a bag and bring it to the counter — we'll match it on the spot. If you'd rather not pull it yourself, call ahead and describe the faucet brand; we'll tell you how far that gets us.