Pump Not Priming? Common Causes, Warning Signs & Proven Solutions

Pump not priming? This means the pump cannot draw water into the system, preventing it from operating correctly. Across South Africa, this is a common problem with centrifugal and surface pumps used in domestic, agricultural, and irrigation applications.

A pump not priming may run dry, fail to deliver water, or struggle to build pressure. Fortunately, most priming problems are caused by system-related issues and can be resolved with a few simple checks.

What Does Pump Not Priming Mean?

Priming a pump means filling the pump casing, as well as the suction line with water before start-up. This removes air from the system, and it also allows the pump to create the suction needed to draw water.

Centrifugal pumps cannot move air effectively. Instead, they rely on water inside the system to operate correctly.

As a result, a pump not priming will often run without delivering water.

Why Is My Pump Not Priming?

When a pump not priming issue occurs, air is usually entering the system or water is not being retained in the suction line.

Typically, this happens because of leaks, installation problems, or faulty components.

Common Causes of a Pump Not Priming

1. Air Leaks in the Suction Line

Air leaks are the leading cause of a pump not priming.

Check for:

Loose fittings
Cracked pipes
Worn seals

Even a small leak can prevent the pump from drawing water properly.

2. Faulty Non-Return Valve (Foot Valve)

A non-return valve prevents water from flowing back into the source.

However, if the valve also fails:

Water drains from the system
The pump loses prime

3. Pump Installed Too High Above the Water Source

Every pump has a maximum suction lift.

Therefore, a pump installed too far above the water level may struggle to draw water and fail to prime.

4. Blocked Suction Pipe or Strainer

Sand, dirt, and debris can restrict flow through the suction line.

This problem is common in:

Boreholes
Dams
Irrigation systems

5. Pump Not Filled with Water

Without water inside the casing, the pump cannot create suction.

This is particularly important for:

New installations
Systems that have been drained

6. Worn Pump Components Causing a Pump Not Priming

Over time, internal components such as the impeller wear down. Consequently, the pump’s ability to generate suction decreases.

7. Incorrect Pipe Installation Causing a Pump Not Priming

Poor pipework can make priming difficult.

Common examples include:

Sharp bends
Poor alignment
Long horizontal suction runs

Fixing a Pump Not Priming

Follow these steps to resolve the problem:

✔ Prime the Pump Properly

First, ensure the pump casing and suction pipe are completely filled with water.

✔ Check for Air Leaks

Next, inspect all suction-side connections and seal any leaks.

✔ Inspect the Non-Return Valve

If the valve is faulty or not holding water, replace it.

✔ Clean the Suction Line

Then remove any blockages from pipes, strainers, or filters.

✔ Check Installation Height

Also confirm that the pump is operating within its recommended suction limits.

✔ Assess Pump Condition

Finally, inspect the pump for wear or damage. In some cases, servicing or replacement may be required.

When a Pump Not Priming May Require a Different Solution

Certain systems experience ongoing priming problems because the pump type is unsuitable.

You may need an alternative solution if:

The suction lift is too high
The water source is inconsistent
The system design does not suit a surface pump

In these situations, a borehole pump may provide a more reliable solution.

Frequently Asked Questions About a Pump Not Priming

Can an air leak cause a pump not priming problem?

Yes. Even a small air leak on the suction side can prevent the pump from creating enough suction to draw water.

Will a faulty foot valve cause a pump not priming issue?

Yes. A failed foot valve allows water to drain back into the source, causing the pump to lose prime.

Can a pump lose prime overnight?

Yes. This often happens because of air leaks, faulty non-return valves, or suction-side problems.

What happens if a pump runs dry?

Running dry can damage seals, increase wear, and shorten pump life. Therefore, the issue should be addressed as soon as possible.

Need Help Fixing Your Pump?

At Pumps Africa, we regularly assist customers across South Africa with pump not priming problems caused by suction leaks, faulty foot valves, blocked strainers, incorrect installation, and worn pump components.

If your pump not priming issue continues, identifying the root cause before replacing equipment can save time and money.

We can help you:

Diagnose the issue
Check your system setup
Recommend the correct pump solution

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Pump Not Priming –Warning Signs & Proven Solutions