Usually in the water used in the distribution there is a percentage of air of about 2%. In case of pressure decrease and temperature increase, the percentage of air decreases and consequently there will be a constant production of free air that expands in the pressure pipes. The vent valves have the function of controlling and managing the air. The vent valves can perform the following functions:
– degassing: the function of removing air;
– volumetric emptying: a large volume of air enters and compensates for the volume of liquid that exits. This avoids dangerous depressions;
– volumetric filling: present air exits to prevent the formation of air pockets;
The best choice for a good operation are the cast iron vent valves, because they are reliable, simple and durable and therefore do not require much maintenance.