What is coefficient of volume?

Coefficient of Volume (Cv) is a factor used in describing the amount of water that will pass through a fully open valve. It describes the flow in gallons per minute (GPM), with a specific gravity of 1, at a temperature of 60 deg F, and a pressure drop of 1 psi. For example, a Cv of 6.0 indicates a flow capability of 6.0 GPM at the above mentioned conditions. For a pressure drop of other than 1 PSI, GPM = Cv*Sqrt(delta P / Specific Gravity), where delta P is in unit of PSI.