Ball Valve

A ball valve has a spherical ball with a hole drilled through its center; rotating the handle 90 degrees either lines up the hole with the flow path (open) or perpendicular to it (closed). The design is simple, reliable, and holds pressure well, which is why it's the go-to for main shutoffs, isolation valves, and anywhere you need a quick, dependable stop.

Ball valves come in two-way (inlet and outlet) and three-way (diverting flow between two outlets) configurations, and are rated for whatever pressure and temperature the application demands—residential water is typically 100 to 150 PSI ball valves, but you'll find them in industrial applications rated much higher. The quarter-turn handle makes it instantly obvious whether the valve is open or closed, and the straight-through port keeps pressure drop minimal compared to gate valves.

The main weakness is that they can get stuck if shut off for long periods or if sediment builds up in the port, and if the seals fail, replacement usually means swapping the whole valve rather than just packing a stem like you can with a gate valve. On new construction and repair work, a quality ball valve is typically cheaper than a good gate valve and lasts longer.