Pump not priming? It means it cannot draw water into the system, which prevents it from operating correctly. This is a common issue across South Africa, especially with centrifugal and surface pumps used in domestic, agricultural, and irrigation systems.
A pump not priming will either run dry, fail to deliver water, or struggle to build pressure. The good news is that most priming issues are caused by system-related problems and can be resolved with the correct checks.
What Does “Priming a Pump” Mean?
Priming a pump means filling the pump and suction line with water before starting it. This removes air from the system and allows the pump to create the suction needed to draw water.
Centrifugal pumps cannot pump air — they rely on water inside the system to function properly.
If air is present, the pump will run but will not move water.
Why Is My Pump Not Priming?
When a pump fails to prime, it usually means air is entering the system or water is not being retained in the suction line.
This can happen due to leaks, incorrect installation, or faulty components.
Common Causes of a Pump Not Priming
1. Air Leaks in the Suction Line
Air leaks are the most common cause of priming failure.
Check for:
- Loose fittings
- Cracked pipes
- Worn seals
Even a small air leak can prevent the pump from drawing water.
2. Faulty Non-Return Valve (Foot Valve)
A non-return valve prevents water from flowing back into the source.
If this valve is faulty:
- Water drains out of the system
- The pump loses prime
3. Pump Installed Too High Above Water Source
Every pump has a maximum suction lift.
If the pump is installed too far above the water level, it will struggle to draw water and may fail to prime completely.
4. Blocked Suction Pipe or Strainer
Debris, sand, or dirt can block the suction line, preventing water from entering the pump.
This is common in:
- Boreholes
- Dams
- Irrigation systems
5. Pump Not Filled with Water
If the pump casing is not filled with water before starting, it cannot create suction.
This is especially important for:
- New installations
- Systems that have been drained
6. Worn Pump Components – Reason For a Pump not Priming
Over time, internal parts such as the impeller can wear down, reducing the pump’s ability to create suction.
7. Incorrect Pipe Installation – Reason For a Pump not Priming
Improper pipe layout, such as:
- Sharp bends
- Poor alignment
- Long horizontal suction runs
can make priming difficult or impossible.
Fixing a Pump Not Priming
Follow these steps to resolve the issue:
✔ Fill the Pump with Water (Prime It Properly)
Ensure the pump casing and suction pipe are completely filled with water before starting.
✔ Check for Air Leaks
Inspect all suction-side connections and seal any leaks.
✔ Inspect the Non-Return Valve
Replace the valve if it is faulty or not holding water in the system.
✔ Clean the Suction Line
Remove any blockages from pipes, filters, or strainers.
✔ Check Pump Installation Height
Ensure the pump is installed within its recommended suction limits.
✔ Inspect Pump Condition
If the pump is worn or damaged, it may need servicing or replacement.
When You May Need a Different Pump
Some systems struggle with priming due to pump type.
You may need a different solution if:
- The suction lift is too high
- The water source is inconsistent
- The system design is unsuitable for a surface pump
In these cases, a submersible borehole pump or alternative setup may be more effective.
Related Pump Solutions For a Pump not Priming
If priming issues continue, the solution may involve selecting the correct pump type:
- Domestic Pump Products → for surface water transfer
- Irrigation Bare Shaft Pump → for agricultural systems
Need Help Fixing Your Pump?
If your pump is not priming and you’re unsure why, it’s best to identify the root cause before replacing equipment.
At Pumps Africa, we can help you:
- Diagnose the issue
- Check your system setup
- Recommend the correct pump solution
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