Glossary
Angle Stop
Also known as Supply stop, Shutoff valve
A valve installed at the water supply line entry to a fixture, allowing you to shut off water to that fixture alone without affecting the rest of the house.
An angle stop is a shutoff valve that connects the main supply line to a fixture's inlet, typically positioned at a 90-degree angle under sinks, toilets, or in wall cavities behind appliances. The valve body is angled so the inlet comes in horizontally from the supply line while the outlet threads vertically up to the fixture connection, saving space and keeping the valve accessible.
They come in two basic types: compression (with a packing nut and stem you turn clockwise to close) and ball valves (with a lever you rotate a quarter turn). Compression stops are cheaper but wear out faster; ball valves are more reliable and faster to operate. Both screw onto 1/2-inch or 3/8-inch supply tubing, and the outlet threads accept flexible supply lines or hard copper.
Every fixture that can be isolated should have one. When a toilet fills valve fails at 3 a.m., or a supply line ruptures, an angle stop lets you shut off just that fixture while the house stays live. If there's no stop valve and something breaks, you're shutting off the whole building. Install one wherever code requires and the customer can afford it.