What is an angle stop?
Updated August 2026
An angle stop is the small valve under a sink or behind a toilet that shuts water off to that one fixture, so a faucet repair never means shutting down the whole house. The name describes the shape. Water enters horizontally from the wall through a 1/2 inch inlet and leaves upward through a 3/8 inch compression outlet, a 90 degree turn with a handle on top. Where the supply comes up out of the floor instead, the identical valve in a straight body is called a straight stop. Count them and a two-bathroom house usually has 8 to 12.
Where it is
Open the vanity cabinet and there are two, hot on the left and cold on the right, with braided lines running up to the faucet shanks. A toilet has one, mounted low on the wall a few inches to the left of the bowl. The others hide in plain sight: a 1/4 inch stop behind or under the refrigerator for the ice maker, one under the kitchen sink feeding the dishwasher, and a pair inside the laundry box. Handle shape identifies the design at a glance. An oval or football-shaped knob is a multi-turn stop with a rubber washer on a rising stem. A short lever is a quarter-turn ball stop, which is the one you want.
What it does
The valve exists so a 20 minute repair stays a 20 minute repair. It also fails in ways that turn one problem into two, which is why plumbers approach a 20-year-old stop carefully. The stem seizes and the handle refuses to move, or it snaps off in your hand. The washer closes most of the way and leaves a trickle, so the faucet keeps dripping onto the parts you have spread across the counter. The packing nut, undisturbed for two decades, begins weeping the moment the handle finally turns, and now the cabinet floor is wet. Multi-turn stops built before the mid-2000s account for nearly all of it, since mineral deposits cement the washer to the seat. Quarter-turn ball stops have almost nothing to seize, cost $8–20, and are worth installing any time a fixture is already apart.
Maintenance
Exercise every stop in the house once a year: close it fully, open the fixture to confirm the water truly stops, then reopen it fully and back the handle off a quarter turn so the stem does not bind in place. The full loop takes about 15 minutes in a two-bath house, and it pairs naturally with the round where you unscrew and soak the aerators (aerator cleaning intervals). Repeat it before any trip longer than a weekend. While the cabinet is open, note the age of the braided supply lines, which want replacing every 5 to 8 years. Any stop that weeps, spins freely, or will not close gets replaced now instead of during the emergency that finds it. Faucets themselves run 15 to 20 years (faucet lifespan), the faucet maintenance checklist keeps the stop, the aerator, and the supply line on one schedule, and ignoring a dripping faucet prices out what waiting costs.
What it costs to replace
A replacement angle stop runs $8–20 for a quarter-turn stop, or $100–200 per valve installed.
OnOtto's photo scan identifies parts like this in your home and builds the maintenance schedule for you. See how the scan works.
Frequently asked questions
My shutoff will not stop the water. What now?
Stop turning it. Forcing a seized multi-turn stop snaps the stem, and then you have an open pipe under a sink with no way to close it. Shut the main instead, drain the pressure through a lower faucet, and replace the valve while the house is off. If the handle turns but a trickle continues, the internal washer is shot and the same replacement applies. Budget 30 to 45 minutes and $8–20 for the part.
Can I replace an angle stop myself?
On copper with a compression fitting, yes. Close the main, open a low faucet to drain, hold the pipe with one wrench and back the compression nut off with another, then slide the new valve over the same pipe with a fresh nut and ferrule and snug it a half turn past hand tight. Push-fit stops at $12–25 skip the wrenches entirely. Call a plumber for soldered valves, galvanized threads, or anything hidden inside a wall.
Quarter-turn or multi-turn: does the choice matter?
It matters on the day you need the valve. A multi-turn stop seals with a rubber washer pressed against a brass seat, and the two fuse together with scale over 10 to 20 years of sitting still. A quarter-turn ball stop rotates a polished ball a quarter revolution and has no washer to weld itself down. Buy a brass body rather than the plastic bargain version, which costs $4 less and cracks under a wrench.