A blockage of the flow in a pump or pipe, caused by an air bubble. An air lock is a restriction of, or complete stoppage of liquid flow. This is caused by air trapped in a high point of a liquid-filled pipe system. Air, being less dense than the liquid, rises to any high points. When pressure is applied, instead of the liquid flowing as it normally would an air lock occurs. Simply put an air bubble reduces the flow in direct proportion to the size of the air bubble. Example: a 1/4” bubble in a 1/2” line reduces the flow by 1/2. It is common that problems with a system are due to a trapped air bubble. To fix this problem be sure to carefully purge the air from the system. See our troubleshooting video on YouTube.