Lead Free Check Valve 700XL Zurn (Wilkins) 1' FNPT x Union FNPT Dual Check Valve. Ideal for use where Lead-Free* valves are required. Designed for installation on potable water lines to protect against both backsiphonage and backpressure of contaminated water into the potable water supply. Assembly shall provide protection where a potential health hazard exists. End connections threaded ANSI B1.20.1