Cla-Val 210-09 and 610-09 Combination Altitude and Back Pressure Valves control the high water level in reservoirs without the need for floats or other devices. These valves modulate to maintain upstream pressure within close limits to prevent overdrawing system supply while filling the reservoir.  When the shut-off point of the hydraulic pilot control is reached, the valves close smoothly without surges. These valves are designed for one-way flow only. 

Used on reservoirs where water is withdrawn through a separate line or through a bypass equipped with a check valve. The valve closes at the desired high water level and reopens for filling when the reservoir head lowers below the shut off level. The valve controls minimum supply pressure to keep from overdrawing supply while filling the reservoir.  Water in excess of system pressure flows to the reservoir at a controlled rate.