Low Water Flow – When the Pump Has Been Operating for Some Time

1. Check Solar Panel Performance
Over time, solar panels can lose efficiency due to connections becoming loose, dirt building up, shading, etc.

• Inspect your solar panels to ensure that they are:
  • Clean and free from dust, bird droppings, leaves, grime, etc. Clean panels gently with a soft brush, a cloth and water if needed.
  • Not shaded — even partial shading on one panel can cause a significant drop in the performance of the whole array.
• The connections are securely connected to each other and not damaged.

• Use a multimeter to check the voltage at the controller:
  • Set you multimeter to detect DC voltage.
  • Place the red (positive) probe on P+ and the black (negative) probe on P- terminals.
    • 24V pump systems should show 35V–55V open circuit voltage (Voc)

• 48V pump systems should show 65V–109V (Voc)
• 72V pump systems should show 80V–140V (Voc)

If voltage is too low, clean the panels and recheck voltage at the P+ and P- terminals.

 

2. Impeller Wear and Clogging Over Time

Sometimes the issue is as simple as debris stuck in the intake.

• For submersible pumps, inspect the inlet screen for grass, dirt, or plastic wrapping and ensure the pump is not drawing in mud or grit from the bottom of the water source.

• For surface mount pumps, check the pump is primed and there are no leaks causing air to be sucked into the pump.

 

2a. Submersible Screw/Helical Rotor Pumps (e.g. bore pumps):

These pumps contain a rotor (metal screw) and a stator (rubber sleeve) that wear out over time.

• The rotor and stator (impeller) should be replaced every 1–2 years depending on your local water conditions (e.g. grit or mineral content).
• Remove the pump and check:
  • The rotor should turn freely inside the stator.
  • It should not feel loose (worn out) or too tight (swollen or hardened rubber). It should turn easily with a firm and gentle grip.
• Rotor and stator should always be replaced as a pair, as they are a matched set.

For instructions, refer to the "How to Replace an Impeller" section of the user manual.

 

2b. Centrifugal Multistage Pumps

These pumps have multiple spinning impellers and are sensitive to clogging.

• Check the inlet screen and impellers for blockages (grass, grit, algae, etc.).
• Running the pump backwards can help clean out the impellers if they are not badly clogged.
  • Run the pump backwards for 5–10 minutes.
  • Switch back to forward for 5–10 minutes.
  • Then reverse again one more time.

To reverse the pump’s running direction:

1. Turn the solar isolator off.
2. Open the controller and take a photo of the pump’s power cable wiring.
3. Swap the wires on the V and W terminals with each other.
4. Turn the solar isolator on.

Note: Be cautious and contact Commodore Australia if you are unsure of this process.

 

If the impellers remain clogged, you may need to disassemble and clean the pump.

• This involves removing and reassembling multiple internal parts in the correct order.

• Contact Commodore Australia on 1300 669 256 for detailed guidance.

 

2c. Single impeller Centrifugal Pumps

These pumps have a single spinning impeller that can be sensitive to clogging. To check the impeller, you will need to disassemble the pump to access the impeller for cleaning.

Contact Commodore Australia on 1300 669 256 for detailed guidance on your specific pump model.

 

3. Check for Mechanical Damage

Most pumps have the same mechanical concerns that are common to all types (failed bearings, failed seals, damaged impellers, etc.) however, each type of pump can have specific mechanical concerns depending on their type.

 

3a. Submersible Screw/Helical Rotor Pumps (e.g. bore pumps):

The most common fault for these pumps is the impeller becoming worn out or damaged, however other faults can include failed seals and/or bearings.

• Remove the pump from the water and check:
  • That the motor shaft can turn freely with a clunking sensation as it is turned. The clunking sensation is the motor shaft’s magnets moving between the windings and is normal.
  • That the motor shaft does not wobble side to side.
  • That the seal where the motor shaft comes out of the motor is clean and in good condition.
  • That the base of the motor is clean and in good condition.
  • That the power cable is not damaged where it enters the impeller housing.
  • That the power cable is not damaged along the length that runs through the impeller housing.
  • That the power cable is not damaged where it enters the motor.

3b. Centrifugal Multistage Pumps

The most common fault for these pumps is the motor shaft and impeller coupling having become worn or stripped over time.

• Remove the pump from the water or disconnect the water inlet pipe and separate the motor from the pump to check:
  • For wear on the motor shaft spline.
  • For wear on the impeller shaft coupling.
• While separated also check:
  • That the motor shaft can turn freely with a clunking sensation as it is turned. The clunking sensation is the motor shaft’s magnets moving between the windings and is normal.
  • That the motor shaft does not wobble side to side.
  • That the seal where the motor shaft comes out of the motor is clean and in good condition.
  • That the base of the motor is clean and in good condition.
  • That the power cable is not damaged where it enters the cable guide or junction box.
  • That the power cable is not damaged where it enters the motor.

 

3c. Single impeller Centrifugal Pumps

The most common faults for these pumps are the mechanical seal having become worn over time and/or failed bearings.

• For surface mount pumps:
  • Check for leaks around the motor’s front cover, particularly where the motor shaft enters the pump.
  • Check for leaks between the pump body and the motor’s front cover.
• Then, disconnect the water inlet pipe and separate the motor from the pump to check:
  • For damage to the venturi pipe.
  • For damage to the diffuser.
  • For damage to the impeller.
  • For damage to the pump body.

• Remove the pump from the water or disconnect the water inlet pipe and separate the motor from the pump to check:

• That the motor shaft can turn freely with a clunking sensation as it is turned. The clunking sensation is the motor shaft’s magnets moving between the windings and is normal.
• That the motor shaft does not wobble side to side.
• That the seal where the motor shaft comes out of the motor is clean and in good condition.
• That the base of the motor is clean and in good condition.
• That the power cable is not damaged where it enters the cable guide or junction box.
• That the power cable is not damaged where it enters the motor.

 

Conclusion:
Low water flow after long-term operation is usually caused by:

• Dirty solar panels
• Worn impellers or stators
• Clogged inlets or impellers
• Mechanical wear (shaft couplings)

Routine inspection every 6–12 months can catch these issues early and keep your pump running smoothly. If in doubt, contact Commodore Australia’s Technical Support team for further assistance.

Phone 1300 669 256 or email support@commodoreaustralia.com.au