Watts 8 1/2 in x 5 1/4 in Boiler Feed Valve w/Backflow Preventer, FNPT and NPT Union – B911-M3
Combination backflow preventer and feed water pressure regulator in one pre-assembled unit, this WATTS boiler feed valve with backflow preventer is for use in residential and commercial hydronic heating systems. Model provides make-up water to the boiler and can prevent backflow when the supply pressure falls below the system pressure.