What to check when your pool pump will not prime
Common causes include low water, an empty skimmer, blocked baskets, a closed valve, a leaking pump lid seal or air in the suction pipe. Do not leave the pump running without water: it can quickly be damaged.
Written and edited by: Pool Explained editorial team
Check the water level, valves and baskets
The water must be high enough to prevent the skimmer from drawing in air. Switch off the power, clean the skimmer and pump baskets, and check that the suction valves are correctly open.
Inspect the pump lid seal. It should be clean, undamaged and correctly seated. Use only a lubricant approved by the manufacturer; an unsuitable product can damage the seal.
Fill the pump housing according to the instructions for that model. If the pump does not establish flow within the specified time, switch it off and continue checking rather than letting it run dry.
Persistent bubbles usually indicate an air leak
Large bubbles beneath the clear lid or air coming from the return jets usually enter on the suction side. Check the lid, drain plugs, valves, joints, skimmer and suction hose.
A joint may draw air in while the pump is running without leaving a wet patch when it is off. Bubbles and loss of prime are therefore often more useful clues than visible drips.
If the pump is full of water but return flow is weak, check the filter, valve positions and the impeller for a possible blockage. Assess the pump and filter together, not as separate pieces of equipment.
Leave electrical and mechanical faults to a technician
If the motor only hums, trips a protective device, overheats or smells of burning, stop trying to run it. A qualified technician should check the capacitor, motor, impeller and power supply.
Once flow is restored, record the clean-filter pressure, the appearance of the water in the pump basket and the strength of the jets. Next time, these references can help you spot a change before the pump loses prime completely.
