Air Valve

The presence of free air in pipeline can reduce the severity of water hammer considerably. Air in a rising main, whether in solution or in bubble from can have number of ill effects
• Cavitation - The formation of vacuous cavities which subsequently rapidly collapse and erode the pump or pipe
• Headloss - Accelerating water past air pockets formed in pipes, leading to head losses
• Other forms may include surging, Corrosion, reduced pump efficiency, malfunctioning of valves or vibrations
A pipeline designer therefore has to factor in all the aforesaid, the critical level of permissible vaccum inside a 
pipeline to prevent collapse vis-a-vis the suction and discharge capacity of an air valve (curves on request) before 
deciding upon the type, size, spacing and location of these air valves.