Pool Pump Not Priming? Common Causes and How to Fix Them

Pool Pump Not Priming? Common Causes and How to Fix Them

A pump that won't prime runs but doesn't move water. You'll usually see an empty or bubbling pump basket, hear the pump labouring, and notice little or no flow coming back through the return jets. It's one of the most common calls we get, and most of the time the cause is simple.

First rule: turn the pump off. A pump running dry heats up fast. It can cook the mechanical seal and even warp or melt plastic fittings, which turns a five-minute fix into a repair bill.

1. Check the water level

If the water drops below the middle of the skimmer opening, the skimmer sucks air instead of water and the pump loses prime. This is the number one cause in warm, windy weather. Top the pool up to the middle of the skimmer opening and try again. See why you must check your water levels.

2. Empty the baskets and clear blockages

A skimmer or pump basket packed with leaves starves the pump of water. Empty both, and check the skimmer's floating weir door isn't stuck shut. If you have a suction cleaner plugged into the skimmer, check the hose isn't full of debris or sucking air through a split. Our article on emptying your skimmer basket covers the basics.

3. Check the pump lid and O-ring

The pump lid has to seal airtight. A cracked lid, a dry or flattened O-ring, or a lid that isn't screwed down evenly will let air in. Take the O-ring off, wipe it and the groove clean, and coat it lightly with a silicone-based O-ring lubricant (not petroleum jelly, which can make the rubber swell). If the O-ring is stretched, flat or cracked, replace it.

4. Look for air leaks on the suction side

Any leak between the skimmer and the pump pulls in air rather than letting water out, so you won't see a drip. Common spots are loose unions either side of the pump, a cracked fitting at the pump inlet, and worn valve O-rings. With the pump running, steady streams of bubbles in the basket or return jets point to an air leak. Hand-tighten unions and check each valve is fully open to the skimmer.

5. Prime the pump by hand

  • Turn the pump off at the power point.
  • Remove the pump lid and fill the pump pot to the top with water from a hose or bucket.
  • Refit the lid with a clean, lubricated O-ring and tighten it evenly.
  • Open the air release valve on top of the filter.
  • Turn the pump on. Once water spurts steadily from the air release, close it.
  • If the basket hasn't filled within a couple of minutes, switch off and repeat — don't let it run dry.

Pumps that sit above the water level, or a long way from the pool, can take a few attempts to prime after cleaning.

Still not priming?

If you've done all of the above and the pump still won't hold water, there may be a cracked pump housing, a failing seal or a suction leak underground. That's a job for a technician. Our team can diagnose it and repair or replace the pump if needed — see our pool equipment repairs service, book online, call (07) 3857 8530, or drop into our shop at 304-306 Junction Rd, Clayfield.