Short definition
A cartridge faucet uses a sealed, cylindrical insert — the cartridge — to control hot/cold mixing and shutoff in a single replaceable part. It’s the dominant modern design for kitchen and bath faucets. When a cartridge faucet drips, you replace the cartridge, not the faucet.
What it is
The cartridge is a cylinder (brass body, plastic body, or hybrid) holding internal seals, a moving spool or stem, and porting that meters water based on handle position. The faucet body itself is mostly a housing — water enters from the supply lines, passes through the cartridge, and exits up through the spout. Pulling the cartridge out and dropping a new one in restores the faucet to factory-new internally.
Three brand families cover most of what’s installed in WA homes:
- Moen Posi-Temp cartridges — 1222 (single-function shower) and 1225 (with volume control). Common in 1990s-and-newer tubs, showers, and lavs. Need the Moen cartridge puller (104421) to extract when seized.
- Delta RP-coded cartridges. Pop free once the bonnet nut and any retaining hardware are off; usually no special tool.
- Price Pfister cartridges. Often have a separate retaining clip in addition to the bonnet.
For tub and shower applications, the cartridge often integrates a pressure-balance spool to satisfy ASSE 1016 / UPC 408.3 anti-scald requirements.
Why it matters to a homeowner
Cartridge replacement is the most common faucet repair in modern homes. The good news: it’s a $20 to $60 part and usually a 30-minute DIY job if the cartridge isn’t seized. Shut off water at the angle stops, pull the handle, remove the bonnet or retaining clip, lift the cartridge out, and drop a new one in. Match the brand and the model.
The bad news: in WA hard-water service areas, a Moen cartridge that’s been in the wall for 15 years is often mineral-locked into the brass body. That’s why the Moen cartridge puller exists — and why you should not try to pry one out with channel-locks. The brass body is thinner than it looks, and a cracked body means opening the wall.
If you installed a faucet and hot is on the right (it should be on the left), pull the cartridge and rotate it 180 degrees. Most cartridges have a tab keying their orientation in the body.
Common failure modes
- Hardened O-rings on the cartridge body. Leak at the spout swivel or under the handle. The cartridge itself may be fine; sometimes only the O-rings need replacing.
- Stuck spool. Handle hard to turn or stuck in one position. Usually scale or debris from supply work; cartridge replacement.
- Pressure-balance spool fails. Temperature swings or scald when other fixtures run. See anti-scald-valve.
- Mineral lock. Cartridge frozen in the body. Cartridge puller required; do not pry.
Common variants
- Cartridge faucet vs. ball-valve faucet. Ball-valve uses a rotating perforated ball with springs and seats; cartridge uses a sealed cylinder.
- Cartridge faucet vs. ceramic-disc faucet. Ceramic disc is a sub-type of cartridge faucet — the disc pair lives inside a cartridge body.
- Single cartridge vs. dual cartridge. Single-handle faucets use one cartridge; two-handle widespread faucets use two stem cartridges, one for hot and one for cold.
- Pressure-balance cartridge vs. plain cartridge. Only pressure-balance cartridges meet UPC 408.3 in tub/shower applications.