Faucet Cartridge

A faucet cartridge is a self-contained valve unit inside a cartridge-style faucet that controls both the flow of water and its temperature. Unlike older compression faucets (which use rubber washers that compress against a seat) or ball faucets (which use a rotating ball), cartridge faucets have a ceramic or plastic disc cartridge that slides or rotates to mix hot and cold water and regulate flow. Most modern single-handle and two-handle faucets use cartridges.

Types of cartridges

• Ceramic disc: extremely durable — two ceramic discs that rotate against each other. Found in higher-end faucets; last 20+ years but cost $30–$100+ to replace. Chips from debris can cause leaks.
• Plastic cartridge: the most common type in mass-market single-handle faucets (Moen, Kohler, Delta). Lasts 5–15 years depending on water quality. Replacement cartridges cost $8–$40.
• Brass cartridge: found in two-handle compression-adjacent designs; more durable than plastic, less expensive than ceramic.

Signs a cartridge needs replacing

• Faucet drips from the spout even when handle is fully closed
• Handle is stiff or difficult to turn
• Inconsistent temperature — handle position doesn't correspond to expected temperature
• Leaking from the base of the handle (cartridge O-ring failure)

Replacement

Shut off the angle stops under the sink, remove the handle (usually one screw under a decorative cap), extract the cartridge retaining clip or nut, and pull out the old cartridge. Insert the new one in the correct orientation (position matters — the hot/cold sides must align), reassemble, and test. The brand and model of the faucet determine which cartridge is needed — manufacturer websites have cartridge lookup tools. Cost: $10–$60 for the part; a plumber charges $100–$250 to replace a cartridge including parts.