Air valves as self-actuated valves play an important role which is the venting of the trapped air in the main and supply lines. In these types of valves, the fluid flow activates the venting operation. A large venting orifice allows large volumes of air to be released on start-up and enters the pipe for vacuum breaking on shut down. A small venting orifice allows air bubbles to be released under the fluid pressure.

It’s strongly recommended to install air valves in high points of the pipeline, after pumps and control valves.
Also for flat pipelines, it’s required to consider air valves in each 500 to 1000 meters.