Symptom
Cause
Remedy
There are seal failures within a 1–year
period or less in a closed system.
Excessive dirt, sand and oxides
Clean the system.
Excessive or improper water
treatment
Check for proper water treatment
recommendations from pump
manufacturer.
Pump Cavitation:
1. Improper selection
2. Compression tank location
1. Check pump operation on its
curve — overloading
2. High head pump must have
compression tank on suction
side of pump.
Excessive temperatures
Check the type of seal and maximum
operating temperature from the
manufacturer.
Pumps run without fluid
Pumps must be primed before
operation.
There is seal pitting, oxygen
corrosion, magnetic iron oxide.
Caused by wear and excessive
amounts of free oxygen.
Check if system has a constant leak.
Fresh water feeding carries oxygen
into the system.
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
18
NRF
™
-25,36,45/NBF
™
-25,36, and 45 Circulator Installation, Operation, and Maintenance Manual
