Ball valves, also referred to as shut-off valves, are usually increasingly present in newer homes. Ball valves make use of a handle to manage the placement of the hollow, perforated sphere inside the mechanism. When the handle is turned, the outlet immediately opens or closes the stream flow. You can say by the handle placement if the dual wafer check valve is opened or closed: when open, the handle lies flat, in alignment with all the flow, so when closed, the handle is perpendicular for the flow. A gate valve is mostly used to completely turned off fluid flow or, within the fully open position, provide full flow within a pipeline. Thus it is utilized either inside fully closed or fully open positions. A gate valve consists of your valve body, seat and disc, a spindle, gland, as well as a wheel for operating the valve. The seat along with the gate together perform the function of shutting off of the flow of fluid. A typical gate valve is shown in Figure 12.9. Ball valves be more effective at forming a strict seal and also have more reliability and longevity than gate valves, but usually are more expensive. They tend to be used for shutoff and control applications. Because ball valves can open and shut immediately, they may be more likely than gate valves to cause water hammer. When a valve is quickly closed on water moving at high-pressure through pipes, there may be shock waves over the plumbing that make a hammering sound. Under high enough pressure, water hammer may cause a pipe to weaken and break. For that reason, users are encouraged to turn the ball valve lever slowly to prevent water hammer. Because with their excellent operating characteristics, ball valves are useful for the broadest spectrum of isolation applications and are avalable in a wide range of sizes and materials and are avalable in full fl ow and full through conduit. Advantages - quick acting, straight through fl ow either in direction, low pressure drop, bubble tight disconnect & operating torque, easily actuated. Disadvantages - temperature limitiations on seating material, long “relative” one on one dimension. The butterfly valve derives its name through the wing-like action with the disc which operates at right angles towards the fl ow. It’s main advantage is usually a seating surface which is not critical. It is made for fl ow isolation. The disc impinges against a resilient liner to produce bubble tightness with low operating torque. Compact along with a simple construction, butterfly valves facilitate easy pipe arrangement. Due to disc, they've already slightly reduced fl ow characteristics. Advantages - quick acting, good regulating characteristics, compact & light, low pressure isolation.