Valves with a "Full Port" have an internal seat diameter that is the same as the nominal pipe size, i.e. a 1 inch pipe size valve with a full port has a 1 inch diameter seat. Valves with a "Reduced Port" have an internal seat diameter that is smaller than the nominal pipe size.

The valve's flow coefficient, Cv, is a value that is determined by flow testing for each valve size. Full port valves will have have a higher Cv than reduced port valves. The Cv rating for each valve is listed in the tables found in the valve catalog.

The definition of Cv is the # of gallons of water that will flow through the valve with a 1 PSI pressure differential when the valve is open.

The equations below can be used to determine:

The CV factor is the number of U.S. gallons per minute that will pass through a valve with a pressure drop of (1) PSI.