Air release valves (ARVs) are used to help resolve air entrapment issues. ARVs are typically located at high point elevations in force mains. The ARV released any entrapped air caught at the high point of the system (see image below 1). This air can come from pressure changes, the pumps, through any openings, and/or through fittings. There is air trapped at high point elevations because air is lighter then water and there is nothing forcing it down the pipe system. If this air is left in the system it can reduce efficiency or can cause water hammering. In more extreme cases it can cause a total “air lock” within the system. ARVs are also used in a lift station design when the piping leaving the system has a high point. For example, the force main may be slightly down hill or it could be an industrial site where the piping comes out the top but then descends again to be underground (see picture below). This is typically done so that the valves and pressure gauges can be above ground to help aid in maintenance. ARVs can also be placed inside a valve vault of the lift station for easy access for maintenance. Without the ARV, cavitation can occur along with the other problem listed above causing damage to the lift station and pumps.