Pool pump not suctioning: causes and professional solutions

If the pool pump does not suck in water or fails to prime, the filtration system may not work properly.

This is one of the most common maintenance problems and, although in many cases it is due to a minor fault (air, dirty prefilter, low level), it can also indicate major pump wear or a problem in the suction line.

Main reasons why the pool pump does not suck in the pool

As pool pump professionals, we explain the most common causes, how to diagnose the origin of the failure and when to replace the pump with a modern and efficient model.

1. Air inlet in the suction pipe

This is the most common cause. If air enters at any point, the pump rotates, but cannot generate the necessary vacuum to draw in water.

You will know that the pool pump is not sucking because of air in the piping if there are bubbles in the prefilter cover, you hear noise (here we explain what happens if the pool pump makes noise, but does not work) hollow inside the pump or the pump is unprimed after a few minutes.

The professional solution to this problem is to check the o-rings, lubricate them with neutral petroleum jelly, close the lid properly and make sure the water level is halfway up the skimmer.

To find out how to do this, you can use our how to remove air from pool pump how-to guide.

In case the pool pump is above the water level, it is highly recommended to add non-return valves, both at the inlet and outlet of the pump. This way, when the pool pump stops, the pump is not completely drained, making it easier to prime the next filtration cycle and preventing the pump from running empty.

2. Clogged prefilter or broken basket.

If the prefilter is full, the pump cannot generate suction. Leaves, insects, lint, small stones, hair and organic debris are typical causes of clogging.

If the pool pump is not suctioning due to clogging, you simply turn it off, clean the prefilter and replace the basket if it is damaged.

3. Blocked or dirty turbine

Many times the problem is not on the outside, but inside the pump. The turbine can be filled with grass strands, fine sand, lime residue, hair or plant fibers.

As a result, the pump works, but does not draw in enough water. This can be solved with an internal turbine cleaning. However, if you are inexperienced, it is best to have a technician do it.

4. Filter saturated or with excessive pressure.

Although it may seem counterintuitive, a dirty filter can prevent the pump from suctioning properly because it increases the resistance of the circuit.

If the pressure gauge is in the red zone, you know for sure that there is overpressure. As a consequence, the pump works forced and can lose its prime.

The solution is to wash/rinse the sand filters or clean/replace cartridge.

5. Incorrectly positioned valves

The valve is a common cause if the pool pump is not sucking. It is, in fact, a very frequent mistake after cleaning or seasonal changes.

Valves may be partially closed or misconfigured after emptying. In this case, the solution is to verify that the skimmer, bottom and Automatic Cleaner are open as appropriate.

6. Motor problems: condenser, bearings, or wear.

When the motor runs, but does not suck, there may be:

• Lack of power due to damaged capacitor
• Shaft rotating with difficulty
• Motor weakened by age or heat
• Deteriorated motor seal with internal leaks
• In older pumps, this is usually the most likely cause.

Our professional recommendation if your pump is more than 8 years old is to replace it with safe and efficient pool pump models.

Quick guide to why pool pump is not suctioning

When to repair a pool pump that won’t suck and when to replace it

You can repair it if:

• The pump is relatively new.
• There is only dirt or poor sealing.
• The failure is simple (o-ring, prefilter, valve).

You have to change it if:

• The pump is more than 8-10 years old.
• It has chronically lost strength.
• It consumes a lot of electricity. Read our guide on pool pump consumption for more information.
• Frequently overheats.
• Will not start without assistance.
• There is wear on turbine or motor.

In case of replacement, we recommend modern ESPA models, with high energy efficiency and excellent performance:

• ESPA Silen I / Nox, for small and medium-sized pools.
• ESPA Silen S / Silen S2, for higher flow and lower consumption.
• ESPA NoxSalt, for pools with salt chlorination.

For more information, visit our guide on which pool pump you need.

Frequently asked questions about why the pool pump is not sucking in

Why is the pool pump not sucking, even though the motor is running?

The most common is air inlet or clogged prefilter. Check o-rings, lid, water level and basket.

What happens if the pump does not fill at startup?

It means that it is not priming. The most frequent causes are: low level, poorly closed lid, dry gasket or leakage in the suction line.

Why doesn’t the pump suck water from the Skimmer?

May be due to: closed skimmer valve, full basket, air in the piping or dirty turbine. If the bottom does suck and the Skimmer does not, it is almost always the valve or a clog.

My pump does not suck and only makes bubbles, what does it mean?

Air is coming in. Lubricate the o-ring, clean the cap seat and check fittings on the suction.

What do I do if the pump constantly loses prime?

Indicates a leakage problem. Check the lid o-ring, bottom plug thread, suction lines and water level.

Can an old pump lose suction capacity?

Yes. Over the years the motor loses power, the bearings wear out and the turbine may deform or corrode. This directly affects the flow rate.