The integral design combines a cartridge style backflow preventer with a cartridge style feed valve into a unique one piece body configuration. Designed for use in hydronic heating systems the dual check backflow prevents heating system water from flowing back into the supply water piping if the supply pressure falls below the heating system pressure. The boiler feed valve automatically fills or refills the closed heating system to the desired cold fill pressure. Both the back-flow and the feed valve contain cartridges that can be serviced or replaced without draining the entire heating system - Adjustable pressure setting