Closes the supply at the tank's Maximum level and opens it at the Minimum level. The fixed water columns represents the pilot's inertia (variable according to the water head's rangeability of between 0.3 and 1 m).
The equipment is non-return. The basic valve is installed at the foot of the tank, the altitude pilot valve is mounted on the basic valve and is connected to the tank by a branch (not supplied) for measuring the depth of water.

- Level rangeability: 3 to 20 m of water head