A full port zone valve is true to it's pipe size. A 3/4" zone valve full port is true 3/4" throughout the bore, therefore the CV value the valve can handle is higher than a valve that is not full port. In other words, the pressure drop through a full port valve is a lot less than with a valve that is not full port.
Zone valves including Taco zone valves, Honeywell zone valves and full port zone valves can be found at www.supplyhouse.com
