This can occur when an attempt is made to pump more water than is available.
It can occur when drafting, from the booster tank, when operating from a hydrant, or when relay pumping.
When residual pressure approaches 0PSI and the impeller speed remains constant, the pressure at the eye of the impeller decreases. As this occurs, water temperature will increase at the impeller eye and create water vapor. The vapor condenses as it passes through the impeller vanes.
This results in the characteristic “pebbles in the pump” sound.
“running away” from the water.
If this condition is allowed to continue, serious damage can occur.
The earliest indication of ______ is fluctuating PDP.