Reduced Pressure Zone Assembly with OS&Y and Flood Sensor. Series C400 Reduced Pressure Zone assembly provides protection to the potable water system from contamination in accordance with national plumbing codes. The series is normally used in health hazard applications for protection against backsiphonage, backpressure and the fouling of either check valve. Series C400 features Lead Free* construction to comply with Lead Free* installation requirements. Includes a flood sensor to detect excessive water discharges from the relief valve. The flood sensor relays a signal that triggers a multichannel alert (call, email, text) to notify personnel about potential flooding.