Engineering
How Centrifugal Pumps Self-Prime and Why They Sometimes Fail To
Quick fact
A standard centrifugal pump cannot push air; it simply churns it without creating pressure. Self-priming pumps get around this by trapping a small reservoir of water in the casing, which creates the vacuum needed to draw liquid up the suction pipe.
Why this is interesting
You've probably seen a pump that 'just won't start'—it spins but moves no water. The culprit is often a tiny pocket of air that stops the pump from working at all.