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When a Flygt N-pump runs but wastewater flow is low, first compare measured flow and head with the original design duty. A partial blockage is only one possible cause: low liquid level, a closed valve, a discharge restriction or a control fault can produce similar symptoms. Do not order an impeller from symptoms alone.
Which signs suggest a blockage?
Longer emptying times, changes in current, repeated trips or new vibration after solids enter deserve investigation but do not establish a diagnosis by themselves. Record wet-well level, running current, flow or emptying time, discharge pressure and alarm history.
What should be checked first?
- Stop and electrically isolate the pump. Before entering a wet well, apply the precautions in the exact Flygt model manual and the site confined-space procedures.
- Check level sensors, valve positions, the check valve, discharge piping and upstream screens. Confirm that the pump is correctly connected to the discharge and compare the duty point with the selection curve.
- If no system-side cause is found, have qualified personnel lift the pump and inspect the inlet, impeller and volute for fibres, grit, damage or clearance issues. Clean, adjust clearances and restart only under the model-specific manual. Never reach into an energized pump.
Blockage or a system fault?
A pump may keep running with a partial blockage, but discharge resistance or an incorrect level-control setting can also reduce flow. After safe cleaning or system correction, remeasure flow, head and current. If the problem continues, investigate wear, rotation and the original selection.
What should an enquiry include?
Send the complete Flygt model, serial number, impeller code, nameplate and damaged-part photographs, liquid and solids details, installation arrangement, measured flow and head, current, alarms and inspection findings. The impeller and wear parts must match the exact hydraulic version; price depends on the confirmed configuration and scope.
Frequently asked questions
Does N-technology mean that a pump can never clog?
No. Self-cleaning hydraulics help reduce common solids buildup, but unusual debris, wear and system faults still require investigation.
Should the impeller be replaced as soon as flow falls?
No. First check valves, piping, controls and the duty point. Inspect the pump and confirm the part number before replacing anything.
Flygt product catalog · Flygt N-pump selection guide · Request a parts identification review