Watts series 9d backflow preventer 3/4 '' -LRB- 0061888 -RRB- series 9d double check valves with next-to-last atmospherical vent the run flow of white-hot or unheated contaminated water from entering into the drink water supply. It of a brass body with unsullied steel intragroup parts, intrinsic strainer, and two long, tight-sealing, and rubber check valves. Series 9d is for never-ending pressure, non-health hazard applications in smaller supply lines, specified as laboratory equipment, processing tanks, sterilizers, dairy equipment, and specifically for boiler feed lines. working pressure : 25psi -LRB- 172kpa -RRB-, supreme working pressure : 175psi -LRB- 12.06 Bar -RRB- watts series 9d backflow preventer 3/4 '' -LRB- 0061888 -RRB- features : ; 1/2 and 3/4 in. -LRB- 15 And 20 mm -RRB- ; typical line-sized construction the check modules to raw boost allowing dirt and debris to pass more freely reducing check fouling ; unsullied steel intragroup parts ; supreme flow at contrabass pressure drop ; provided with with union connections to facilitate removal and replacement for maintenance ; compendious for economy joint with performance ; design simplicity for comfortable maintenance ; can be installed vertically or horizontally.