The ball valve is a very common type of valve. It is found in many different applications including some swimming pool systems. While pool professionals prefer the Jandy valve, this valve is sometimes found on pool systems due to its lower cost.
The ball valve has a very simple design. It has a ball on the inside of the valve that has a big hole going through it. As you turn the valve handle, it moves the ball on the inside of the valve.
When the handle is inline with the piping (as shown in the picture), the inside ball is situated in such a way that water is allowed to flow through the valve. When the handle is crossways with the valve, the ball is “crossways” to the valve body so that water is not allowed to flow through the valve.
Ball valves are very common and you can find them in your local hardware store. If you pick one up and look at it, you will see exactly how they operate.
Ball valves are not serviceable. When they get difficult to operate or the handles break off, you have no choice but to replumb the entire manifold. This is why pool professionals prefer the Jandy valves.