Direct-type boiler and chiller fill valve assemblies with integral backflow preventer and system pressure regulator are used to control the inflow of water into heating and cooling systems to ensure sufficient system pressure. Devices protect the potable water supply against backflow due to backpressure and backsiphonage.

Devices incorporate two independent check valves in series separated by a means of discharging to a drain by way of a valve and air gap, a means to automatically control flow based on a pressure range, and a means of atmospheric venting to allow drainage. Devices shall only be installed in the Inlet vertical up- outlet vertical down (VUVD) orientation. Check valves shall be force-loaded to a normally closed position.