Pumping System Trouble Analysis Guide

Pump Service Manual & Troubleshooting Guide 

Table of Contents

No circulation Set screw not tight, coupler loose on shaft

Impeller slipping on shaft

Air-bound system

Air-bound pump

Broken pump coupler

Clogged impeller on piping

System valve closed

Pump electrical circuit broken

Tighten set screw in recess in the shaft

Check to see if impeller is placed on the key way of the shaft

Tighten impeller nut

Vent system

Vent pump casing

Replace; check alignment

Locate and remove obstruction


Check all related low and line voltage circuits

Air-bound system

Air-bound pump

Clogged impeller or piping

Clogged strainer

Pump impeller damaged

Insufficient NPSH (Net Positive Suction Head)

Pump too small

Partially air-bound pump

Pump running backwards (three phase)

Improper motor speed

Vent system

Vent pump casing

Locate and remove obstruction

Remove and clean screen


Lower pump or raise pressure or relocate

Replace pump or impeller

Vent pump casing

Reverse any two motor leads

Check wiring and voltage

Pump or system noise Entrained air

Pump cavitation

Pump misalignment

Worn pump coupler

Excessive water velocity

Poor foundation (base-mounted)

Pipe vibration

Vent system

Lower pump or raise pressure or relocate
(See note)

Re-align pump

Replace; check alignment

Install balancing cocks or parallel piping

Provide rigid foundation with adequate

Provide adequate pipe support

Premature failure of
pump components
Improper pump (size or type)

Improper pump location

Pump misalignment

Excessive water treatment

Over-oiling of pump


Pump operating close to or beyond

end point of curve

Excessive piping load




Check manufacturer’s instructions

Check manufacturer’s instructions

Check manufacturer’s instructions

Balance system

Provide proper pipe support

Seal failures within
1 year period or less in a closed system
Excessive dirt, sand and oxides

Excessive or improper water treatment

Pump Cavitation:

1. Improper selection

2. Compression tank location

Air-seal without lubricant (water)

Excessive temperatures

Pumps run without fluid

Clean system

Check for proper water treatment recommendations from pump manufacturer

Check pump operation on its curve-overloading

High head pump must have compression tank on suction side of pump

Vent air from pump volute

Check type of seal and maximum operating temperature from manufacturer

Pumps must be primed before operation

Seal Pitting

– Oxygen corrosion

– Magnetic iron oxide

Caused by wear and excessive amounts of free oxygen Check if system has a constant lead
Fresh water feeding carries oxygen into the system
NOTE: Cavitation can be recognized by low rumbling or sharp rattling noises. The 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.