Troubleshooting & Maintenance
Centrifugal Pump Troubleshooting Guide | Fix Vibration, Cavitation & Low Flow
When a Centrifugal Pump “Sounds Wrong”, It Usually Is
Centrifugal pumps are reliable workhorses, but when something goes off—noise, vibration, low flow, seal leaks, overheating—it’s usually a warning sign that’s getting worse, not better.
This guide helps you identify the most common centrifugal pump issues, what typically causes them, and what you can do before downtime becomes expensive.
If you’re unsure, ASW Engineering can help you troubleshoot, repair, or select a better-fit replacement pump for your application across South Africa and multiple regions in Africa.
Quick Troubleshooting Checklist (Start Here)
Before diving into deeper causes, check the basics:
- Is the pump primed (full of liquid)?
- Is the suction valve fully open?
- Is the discharge valve position correct?
- Is the pump rotating in the correct direction?
- Are strainers or filters blocked?
- Is the suction line drawing air (leaks, vortexing, low tank level)?
- Has anything changed recently (new product, new temperature, higher viscosity)?
Small changes often create big pump problems.
Problem 1: Low Flow or Low Pressure
What you see:
- Pump is running, but the system is underperforming
- Low discharge pressure, weak flow, poor process results
Most common causes:
- Blocked suction strainer or clogged filter
- Air trapped in suction line or pump casing
- Wrong impeller size or worn impeller
- Discharge valve partially closed
- Pump running too slow (VSD settings)
- System curve changed (more restriction, new pipework, scaling)
What to do:
- Check and clean suction strainers/filters
- Confirm the pump is fully primed and vent air if required
- Verify suction valves are open and suction head is adequate
- Inspect impeller wear (especially in abrasive service)
- Confirm duty point: flow (m³/h) + head (m) + liquid details
Common “hidden” cause:
If the liquid became thicker (higher viscosity) or the temperature changed, a pump that used to work can suddenly struggle.
Problem 2: Pump Loses Prime (Works… Then Stops Pumping)
What you see:
- Pump runs fine briefly, then flow drops off
- You may hear gurgling or irregular operation
Most common causes:
- Air leaks on suction line (even tiny leaks matter)
- Suction lift too high (pump can’t pull reliably)
- Vortexing in tank/sump (air being pulled into suction)
- Foot valve issues (if installed)
What to do:
- Check suction pipe joints, flange gaskets, and mechanical seals
- Increase liquid level or reduce suction lift
- Improve suction conditions (straight pipe run, correct suction sizing)
- Add anti-vortex plate or modify tank suction arrangement
Problem 3: Cavitation (The “Gravel” Sound)
What you hear/feel:
- Crackling or grinding noise like stones in the pump
- Vibration increases
- Performance becomes unstable
- Long-term damage to impeller
What cavitation usually means:
The pump is not getting enough pressure at the suction side. The liquid partially “flashes” into vapour bubbles and then collapses violently inside the pump.
Most common causes:
- Insufficient NPSH available (not enough suction pressure)
- Suction line too small / too long / too many bends
- Blocked suction strainer
- Liquid temperature too high
- Pump speed too high
- Suction valve not fully open
What to do:
- Reduce suction losses: bigger suction pipe, fewer bends, shorter run
- Clean strainers/filters
- Reduce pump speed (if on VSD)
- Lower the pump closer to the liquid source (increase suction head)
- Confirm the pump is correctly sized for the duty point
Important:
Cavitation is not “normal noise.” If it continues, it can destroy impellers and seals.
Problem 4: Excessive Vibration
What you notice:
- Pump “shakes”
- Pipework rattles
- Bearings fail early
- Mechanical seal leaks
Most common causes:
- Misalignment between motor and pump coupling
- Soft foot or poor baseplate installation
- Cavitation (very common)
- Imbalance (impeller damage, buildup, wear)
- Operating too far from best efficiency point (BEP)
What to do:
- Check alignment and coupling condition
- Inspect foundation/baseplate for looseness
- Verify suction conditions (rule out cavitation)
- Inspect impeller for damage or product buildup
- Confirm the pump is not oversized and throttled too hard
Problem 5: Mechanical Seal Leaks
What you see:
- Drips around seal area
- Spray or visible leakage
- Seal flush problems
Most common causes:
- Dry running (even briefly)
- Misalignment and vibration
- Incorrect seal material for chemical/temperature
- Seal faces damaged by solids/abrasives
- Incorrect seal flush arrangement
What to do:
- Confirm pump is primed and never running dry
- Check for vibration/misalignment
- Confirm compatibility of elastomers and faces
- Improve filtration/solids handling if needed
If leaks are a major safety risk:
Consider magnetic drive or canned motor (hermetic) pumps for true leak-free operation.
Problem 6: Pump Overheating or Bearing Failure
What you notice:
- Hot bearing housings
- Frequent bearing replacement
- Burnt smell or high motor amps
Most common causes:
- Running against a closed discharge valve
- Poor lubrication / wrong grease
- Misalignment or excessive vibration
- Operating too far off the pump curve
- Dry running or low flow operation
What to do:
- Confirm flow is within the pump’s recommended range
- Check bearing lubrication schedule
- Verify alignment and vibration levels
- Check motor current draw and compare to nameplate
When to Stop and Call for Help
You should stop troubleshooting and call a pump specialist when:
- Cavitation persists after suction checks
- Seals keep failing repeatedly
- You’ve had multiple bearing failures
- Flow/head requirements changed and the pump no longer fits the duty
- You’re handling hazardous, flammable, or toxic liquids
ASW Engineering Can Help You Fix It or Replace It Correctly
If you want fast, accurate support, send us:
- Required flow (m³/h or L/min)
- Total head (m)
- Liquid type + temperature + viscosity (if known)
- Suction conditions (tank level, suction lift, pipe size/length)
- Current pump make/model (if available)
ASW Engineering supplies industrial pumps across South Africa and multiple regions in Africa and can help you troubleshoot performance issues, recommend upgrades, or supply a better-fit pump solution.
Disclaimer: This article is provided for general informational purposes only and does not replace professional engineering advice or manufacturer documentation. Always verify suitability for your specific application and follow site safety procedures. ASW Engineering can assist with pump selection and technical support.