Manual ball valves are commonly used to operate shut-off valves, which control water flow in, for example, plumbing systems. They get their name from the metal ball inside the device, which has a hole through the middle.
When the valve is open, the hole is aligned with the pipes and permits flow. When it is closed, the hole is rotated perpendicular to the flow, shutting it off completely. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's status.
When choosing manual ball valves, pay attention to the way in which they can be attached to the shut-off valve. These methods include compression, push-fitting, threaded ends and solvent cement sockets.
Manual ball valves are also differentiated by the materials they are made from, which include brass, iron, plastic and stainless steel. The application of a manual ball valve is determined by this; for instance, a stainless steel valve is much more capable of withstanding heat than one made from plastic.