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A lever valve is a simple device installed in plumbing systems that provides for the quick and easy interruption of the flow of liquid, gas, or slurry through the plumbing system. The lever is the external component of the valve which is moved to a position perpendicular to the pipe to close the valve completely. The valve itself is actually a ball valve; the term “lever valve” refers to the control mechanism.
All plumbing systems require valves to regulate the flow through its components. When a valve is fully open, the substance flows through it unimpeded; when a valve is closed, passage is completely blocked. Many valves are designed to allow the user to regulate the flow to a high degree of accuracy; for example, the valves with which most people are familiar, the hot and cold water faucets on sinks, generally allow users to open the valve to any degree desired. When controlled by circular controls like wheels, it can take many complete turns of the circle to open or close the valve completely.
In addition to the valves controlling flow from the system, most plumbing systems contain a number of valves that regulate flow within the system. In a common household plumbing system, one of the main reasons for such valves is to facilitate maintenance and repair work on the system. For example, if there's a leak in the system, it must be repaired, which requires shutting off the flow to the area where the leak occurred. A lever valve is an excellent emergency shutoff valve because it requires only a quick 90-degree turn of the lever to shut off flow. When lever valves have been installed in strategic locations within the system, it's possible to isolate one part of the system for maintenance and repair without shutting down the entire system.
A lever valve consists of a lever, which is the external control mechanism, the valve housing, and a sphere through which a hole, or port, has been drilled. The valve housing is wider than the pipe in which it's installed, and contains a cavity within which the ball fits snugly. The alignment of the hole in the ball is controlled by the lever, and when the hole in the ball lines up with the openings in the end of the valve housing, the substance in the pipes flows without obstruction. Turning the ball 90 degrees, so that the hole in the ball is perpendicular to the valve openings, completely shuts off flow through the pipe.
Other types of valves, such as the gate valves which usually operate faucets and sill-cocks, aren't adequate to the job of quickly shutting off the flow through a system because they're designed to modulate flow incrementally, and require many full turns to block flow completely. In addition, lever valves are built with the lever parallel to the flow when open, and perpendicular to the flow when closed. Thus, a lever valve's status — open or closed — is easily visible, which could be of critical importance in an emergency situation, when valuable time could be lost trying to determine the status of a valve with a circular control mechanism.