What is an air lock?
An air lock occurs when large pockets of air are drawn into the inlet side of the water pump. This essentially acts as a void, and can prevent the pump from drawing in water. Not only will this decrease (or even stop) pump performance, it can be very damaging as well. If the air pocket is drawn through the impeller and into an area of high water pressure, the bubbles will collapse and create large shock waves that will severely damage the pump.