Cla-Val Pacific Models 210-02 and 610-02 Altitude Valves control the high water level in reservoirs without the need for floats or other devices. They are non-throttling valves that remains fully open until the shut-off point is reached. These valves close at the high water level, and for return flow, delay its opening until the pressure at the valve inlet lowers to a preset adjustable pressure of one to seven pounds.