Watts Ductile Iron Pressure Relief, Sustaining or Backpressure Control Valve LF920GD

Designed to permit flow when upstream pressure is above the adjustable setpoint of the control pilot, and throttle when upstream pressure falls below the adjustable setpoint. When installed "off the main line" on the branch of a tee, the valve serves as a Pressure Relief Control Valve. It remains normally closed, and quickly opens when upstream pressure exceeds the pilot setting, relieving excess pressure. When installed "in line" connecting two distribution zones, the valve acts as a Pressure Sustaining Control Valve. When upstream pressure falls below the pilot setting the valve throttles to sustain pressure in the upstream zone. When installed "in line" on the discharge of a pump, the valve acts as Backpressure Control Valve. When pump discharge pressure falls below the pilot setting the valve throttles to increase backpressure against the pump.