Troubleshooting

Contact our Technical Service Department at 1-800-888-3743 or by e-mail at techservice@finishthompson.com if you have any questions regarding product operation or repair.

Sealless Centrifugal Pump

General Notes:

  • Do not pump liquids containing ferrous metal fines.
  • If magnets decouple, stop pump immediately. Operating the pump with the magnets decoupled will eventually weaken the magnets.
  • Do not use mismatched drive magnet assemblies (different number of magnets on inner and outer drive magnet assemblies). 

No or Insufficient Discharge

  • Air leaks in suction piping
  • Pump not primed
  • System head higher than anticipated
  • Closed valve
  • Viscosity or specific gravity too high 
  • Motor too large for magnet coupling rating (magnets uncoupled)
  • Suction lift too high or insufficient NPSH
  • Clogged suction line or impeller vanes
  • Motor rotation incorrect (correct rotation when viewed from the fan end is clockwise - except DB3-5.5 models)

Insufficient Pressure

  • Air or gas in liquid
  • Impeller diameter too small
  • System head lower than anticipated
  • Motors speed insufficient (too low) or motor rotation incorrect (correct rotation when viewed from the fan end is clockwise - except DB3-5.5 models)

Loss of Prime

  • Leak in suction piping
  • Foot valve or suction opening not submerged enough
  • Foot valve too small or leaking
  • Air or gas in liquid
  • Foreign matter in impeller
  • Leaking valve. Suction lift too high or insufficient NPSHa.

Excessive Power Consumption

  • Head lower than rating
  • Excessive flow
  • Specific gravity or viscosity too high.

Vibration/Noise

  • Loose magnet
  • Drive magnet rubbing
  • Pump cavitating from improper suction or feed
  • Motor or piping not properly secured
  • Foreign object in impeller

Won’t Prime (SP Series Only)

  • Did not fill housing with fluid before initially starting pump
  • Closed discharge valve (valve should be open or open air vent line)
  • Leak in suction piping
  • Suction pipe not submerged enough (causing a vortex or exposing the end of the suction pipe)
  • Lift exceeds pump ability (see SP11/15 Capabilities section)
  • Suction pipe diameter too large 
  • Specific gravity or local atmospheric pressure (altitude/elevation) not accounted for in lift calculations
  • Mismatch of inner volute and impeller diameter
  • Inner volute o-ring chemically attacked, cut, brittle, etc.
  • Motor rotation incorrect (correct rotation when viewed from the fan end is clockwise)
  • Check valve installed too close to the pump

Primes Slowly (SP Series Only)

  • Mismatch of inner volute and impeller diameter
  • Suction pipe diameter too large (larger than 1 1/2”)
  • Closed discharge valve (valve should be open)
  • Inner volute o-ring chemically attacked, cut, brittle, etc.

Drum Pump

  • Ensure adequate power/air pressure being supplied to motor
  • For electric motors, if a manual circuit breaker is present, push to reset
  • Ensure that the pump and motor model is assembled correctly using the required coupling insert as instructed per the manual
  • Confirm there are no obstructions or restrictions in the discharge hose affecting the performance or flow rate
  • Make sure the application fluid and application parameters fall within the capabilities of the pump/motor combination selected