Plumbing glossary

Ball Valve

A ball valve is a type of shutoff valve that uses a rotating ball with a hole (bore) through its center to control flow. When the handle is parallel to the pipe, the hole aligns with the pipe and water flows freely. Turn the handle 90 degrees — perpendicular to the pipe — and the solid side of the ball blocks the flow completely. Ball valves are the most widely used shutoff valve in residential and commercial plumbing today.

Why ball valves are preferred

Speed: one quarter-turn fully opens or closes — critical in emergencies.
Reliability: far less prone to corrosion seizing than gate valves; the ball and seat resist mineral deposits better than threaded stems.
Low pressure drop: a full-port ball valve's bore matches the pipe diameter, so flow restriction is minimal.
Long service life: quality brass ball valves last 25–50 years without maintenance.

Full-port vs. standard-port

A full-port (full-bore) ball valve has a ball opening that matches the inside diameter of the pipe — no restriction to flow. A standard-port (reduced-bore) valve has a smaller opening, which slightly reduces flow rate and increases pressure drop. For main shutoffs and supply lines, full-port is standard. Standard-port is acceptable for low-flow applications like irrigation branches.

Where ball valves are used

Main water shutoff at the meter or foundation entry
Isolation valves at water heaters, washing machines, ice makers
Zone valves on radiant heating systems
Gas shutoffs (gas-rated ball valves only — never use a water ball valve on gas)

Common failure modes

Ball valves rarely fail catastrophically but can develop stem leaks (a drip around the handle stem) over time. This is usually fixed by tightening the packing nut or replacing the packing. A ball valve that won't fully shut off typically has a worn seat — replace the valve rather than repair it.

Cost

A quality brass full-port ball valve costs $8–$25 for typical ¾" or 1" sizes. A plumber installing one as a new main shutoff charges $200–$500 including parts and water shutoff at the street.