What is an air purge and when is it used?

• A. A method to purge water from the line after use.
• B. A device to seal leaks in a hose.
• C. A method to clean the line with air after charging.
• D. A method to remove air from a new or relocated line before charging to ensure a steady stream.

Answer: (D)

Air purge means removing trapped air from a hose or pipe line before you charge it with water. When a line is new or has been relocated, air can get trapped in high spots or sections. If you start charging the line with water while air is still present, pockets of air can cause an unstable flow, water hammer, or delayed water delivery to the nozzle. Purging is done so that, once you begin delivering water, the flow is steady and continuous.

In practice, you open a purge point at the low point of the line or use a purge valve and allow air to escape as water begins to fill the line, continuing until you get a steady stream of water with no sputtering. This is different from draining water after use, sealing leaks, or cleaning a line with air after charging, all of which describe other procedures.