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7 Reasons Why Pool Pump Won’t Prime and Quick Fixes

Swimming pools are great assets in any property, not only because they add value but because they provide such enjoyment for the whole family. Except, that is, for Dad or whoever is designated to clean, maintain, repair, and keep it in shape! One job that can make you want to do away with the pool is getting the pump to operate after cleaning and backwashing. Why won’t it prime?

The reason the pool pump won’t prime is that it is unable to generate a vacuum strong enough to pull water into the system and begin the circulation of water through the filter and back into the pool. There are several underlying causes, most of which can be quickly resolved.

Priming a pool pump is required so that it has enough water supplied from the intake to begin pulling water from the pool. It’s unnecessary to prime the pump every time it is switched on, and in fact, many pumps are self-priming (which we’ll talk about later). If the pump won’t prime, there are several reasons and remedies to try before calling in the experts. Let’s dive in!

Why Won’t My Pool Pump Prime? The Facts And The Fixes

If your pool pump has been idle for a month or two, or if you’ve interrupted its operation by removing the pump lid, backwashing, or changing the sand in your filter, it must be primed. If it stubbornly refuses, a quick diagnosis of the reasons must be made.

7 Reasons Why Your Pump Won’t Prime

In a nutshell, a pool pump won’t prime fully if there’s a poor flow of water or air is being sucked into the system. In more detail:

Reason 1: The skimmer, where water is being drawn in from the pool, might be blocked with leaves or other debris.

The fix: Clearing the skimmer basket should be a regular task, particularly if your pool is close to trees and plants which shed their leaves.

Pool skimmer issues could prevent your pump from priming. Learn about common skimmer problems here.

Reason 2: The water level in the pool may have dropped so far that it’s below the skimmer box entrance. This happens, sometimes unexpectedly, when there is a lot of evaporation on hot or windy days, when there has been a lot of activity in the pool, or when you’ve done a long backwash.

The fix: It’s easy enough to top up the pool before you prime the pump. Once you’ve done this also check the weir gate, which is the hinged rectangular plate that flips open and closes with the movement of water. If it gets stuck, it will impede water flow into the weir.

Reason 3: The strainer lid allows air to be sucked into the filtration system at this point.

The fix:There is a rubber gasket or O-ring, which may need to be seated correctly. Sometimes a leaf or small twig gets under this ring, causing the seal to be deficient. Ensure the groove holding the gasket is clean, and use suitable grease for seating it. If the O-ring is old or cracked, replace it. The cover itself may be cracked, or it might not have been tightened down sufficiently, so check this as well.

While you have the cover off, also check that the strainer basket is intact. When it’s been allowed to get overfull, it often cracks and let’s debris through to the pump impeller.

Reason 4: There could be a leak in the inlet pipes before the pump. Depending on the installation, there are several bends and joints which are connected and sealed with an adhesive that can fail after a while.

The fix: Check for water dripping from joints when the pump is on. If you find any, that means air will be getting in when the pump is off and will make a full prime impossible. If the pipes are cracked, they’ll have to be replaced, but otherwise, you will just need to clean and re-seal the couplings.

Reason 5: The impeller may be clogged or damaged. If the latter is the case, it won’t be able to drive the water through the system with enough pressure.

The fix: Repair or replace. If the impeller has jammed, you might hear the motor humming but not spinning. There’s the chance it will burn out, so free the impeller immediately – access through the bottom of the strainer box should be relatively easy.

Reason 6: Your pool pump might have reached retirement age. It can last 8 to 10 years, depending on how much work it’s had to do, but 5 years is generally considered a reasonable life span.

The fix: If you hear grinding, whining, or screeching noises, the bearings may have gone, shafts might have worn, and it may be time to replace the motor.

Reason 7: No water is getting into the strainer box.

The fix: Your inlet valves may be closed. I’m embarrassed to admit I’ve been guilty of forgetting this simple step more than once.

Regular maintenance is key to prevent issues like a pool pump that won't prime. Follow our weekly pool maintenance checklist.

Self – Priming Vs. Non-Self-Priming Pool Pumps

Almost all in-ground pools use self-priming pool pumps, which can draw sufficient water through the system to prime themselves after a few seconds. There are situations when they need to be primed by hand, as we’ve discussed in detail above, but it’s not necessary for the rest of the time.

If you have an above-ground pool, the pump is not self-priming because it is almost always situated below the level of the pool, and water flows naturally into the system through gravity feed. These pumps are known as flooded suction pumps.

The Steps To Prime Your Pool Pump

Let’s put everything we’ve mentioned into a logical sequence. At the beginning of summer, after cleaning and backwashing, or if you’ve dismantled the filtration system for repairs and maintenance, these are the steps to prime your pool pump.

  1. Switch off the pump and set the multiport valve to “recirculate.”
  2. Open the air relief valve.
  3. Open the strainer lid, remove all leaves and debris, and check the lid for cracks. Check the O-ring, and the strainer basket, ensuring they are in good condition.
  4. Fill the pump with water, replace the strainer basket and lid, and tighten it securely.
  5. Turn on the pump. Water should begin pumping strongly through the strainer basket within 30 seconds. Water should come through the air relief valve, indicating all air is out of the system.
  6. Close the air relief valve, switch off the pump, and turn the multivalve to “filter” before turning the pump on again.

Conclusion

We’ve detailed seven reasons why your pool pump won’t prime. Hopefully, we’ve provided the fixes to solve the problems and get your pump primed and your filtration system working so you won’t feel the need to fill in your pool!

Learn more about why your pool pump might not be working.