Plastic ball valves shut off the flow of water using a small sphere, or ball, inside the valve. The sphere has an opening inside. When in the "on" position, the opening is in line with the pipe, allowing water to flow freely. When in the "off" position, the opening is perpendicular to the flow of water, stopping the flow completely. In a ball valve, flow is controlled with a lever. Placing the lever perpendicular to the pipe allows water to flow. Moving it at 90-degree angle stops the flow.

Plastic ball valves have several advantages. They are easy to turn on and off quickly, and can be used by individuals who cannot maneuver a wheel-operated valve due to disability. They allow the user to tell at a glance if the valve is open or not. They are durable, rarely freeze even with years of use, provide reliable service, and are extremely versatile. Plastic ball valves are used in home plumbing, industrial applications, oil and gas applications, marine applications, pharmaceuticals, and many other fields.

The primary disadvantage of the plastic ball valve is the requirement of space. In tight applications, you may not have 90 degrees to turn the valve's handle. Also, in rare instances a plastic ball valves can create a water hammer condition.