District News Articles

  2. A routine function performed by the District’s operations staff is bi-annual maintenance of Air-Vacuum (Air-Vac) valves.  An Air-Vacuum valve is a device installed on water mains 12 inches or larger.  Its purpose is to allow air to enter a water main when it is being shut off and drained for maintenance and repairs.  In turn, when the water main is being re-filled the Air-Vac valve allows air to escape from the pipe.  Entrapped air has a force up to nine times greater than the water pressure in the main.  These pockets of entrapped air can cause failures to the water main and if the air pocket travels into a customers’ water service connection it can cause property damage.


    Air-Vac valves are installed in pairs and are housed in vaults throughout the District.  During the bi-annual maintenance Bow Mar operations personnel visit each vault, flush the valve assemblies, and check the valve operation to ensure that proper vacuum and venting actions are taking place.


    Most vaults have one or two vent pipes for air circulation.  In the spring the vent pipes which were wrapped with plastic during the fall maintenance operations to prevent cold air from freezing the valve assemblies are unwrapped to restore fresh air circulation.


    If you have any questions regarding the District’s Air-Vac valve maintenance program, please feel free to contact Scott Hand, Operations Supervisor at 303-979-2333.