Bell & Gossett P86203F NBF 45 Circulator - Manual (Page 19)

NOTICE:
Cavitation is identified by low rumbling or sharp rattling noises. This situation is created
by the lack of available net positive suction head (NPSH). The pressure at some point in
the pump falls below the vapor pressure of the water causing flashing and the formation
of bubbles, which are carried into the volute where the higher pressure causes them to
implode. This can eventually destroy the pump.
Troubleshooting
NRF ™ -25,36,45/NBF ™ -25,36, and 45 Circulator Installation, Operation, and Maintenance Manual 17