· It is the formation of vapor bubbles in the pump casing and is accompanied by a distinctive rattling noise.
· This is the indication of water being drawn more than normal.
· This is the remedy is to reduce the discharge rate.
· Water boils at 100° C at atmospheric pressure (760 mm Hg).
· If the pressure is reduced it will boil at lesser temperature.
· If the pressure is reduced sufficiently, water can start boiling at atmospheric temperature.
· When more and more of water is drawn from the pump, it keeps on reducing pressure at the suction till water starts boiling at the room temperature.
· This creates water vapors and bubbles which enter the impeller creating “Cavitation”.
· This can also happen if there is obstruction in the suction line e.g. blockage in the foot value or suction strainer.