Series S116-5, S1116-5 Backpressure or Sustaining Control Valve with Hydraulic Check Feature is designed to permit flow when upstream pressure is above the adjustable setpoint of the control pilot, and throttle toward closed when upstream pressure falls below the adjustable setpoint. The valve will also close drip-tight when downstream pressure becomes greater than upstream pressure. When the valve is installed in line on the discharge of a pump, it acts as Backpressure Control Valve. When pump discharge pressure falls below the pilot setting, the valve modulates toward a closed position, increasing backpressure against the pump. When the valve is installed in line connecting two distribution zones, the valve acts as a Pressure Sustaining Control Valve. When pressure in the upstream zone falls below the pilot setting, the valve modulates toward a closed position, sustaining pressure in the upstream zone.