Priming The Pump
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The pool pump is the heart of the swimming pool.  Sometimes the pool pump will be on but it is not moving any water.  Pool pumps are designed to pump water and can handle a small amount of air in the system.  If too much air enters the system, the pump may fail to move water or "Loose the Prime".  Air can enter the system in many ways.  It is important to determine why the pump lost it's prime before you try to get it circulating again or you may not succeed.  There are two kinds of pumps - "Self-Priming" and "Flooded Suction".  The majority of swimming pool pumps are Self-Priming however, most pool cleaner pumps are Flooded Suction type.  Basically, if your pump has a strainer basket on it then it is a self priming pump.  Be sure to keep the O-Ring on the pump lid lubricated with "Magic Lube" or petroleum jelly to help the lid seal correctly and to allow easier removal of the lid.  When the pump is operating correctly the pump lid is under suction and the pump will naturally squeeze the lid tight.  It is important NOT to over tighten the pump lid or removal will be difficult.  Some pump lids will accommodate a piece of 2x4 lumber to be used as a "Lever" to help loosen the lid.  It is normal for a pool pump lid to "squirt" water from under the lid when the pump is turned off.  This is simply a result of the water "relaxing" from being under suction.  When the pool pump is operating correctly, it will appear as though there is NO water in the pump.  What you are viewing is 100% water in the pump basket and no air.  With no air bubbles swirling and only water, it appears as if the trap is empty.  Look for debris swirling around or check the pressure gauge on the system to be sure.

Factors that may cause the pump to loose it's prime:

bulletAir in the system - Is the water level low in the pool?  Is a weir (flap) stuck closed inside a skimmer throat?  Is the pump lid on tight and is the O-Ring installed and lubricated?  Are there any breaks or leaks on the suction plumbing?  Was the pool winterized properly?  A broken skimmer line from freeze damage can occur.  Chlorinators that are attached to the suction side plumbing need to be inspected for air leaks.
bulletObstructions - Are the skimmer baskets full of debris and restricting water flow?  Is the main drain covered with leaves or other objects?  Is the pump basket full of debris?  The pump impeller could be clogged with hair or other debris.  Are the suction valves in the open position?
bulletPower Outage - If the power goes out to the pump and then comes back on at a later time, air could have slowly entered the system and caused the loss of prime at the time the pump started back up.

Factors that affect the pumps ability to catch a prime:

bulletPump Location - The further the pump is from the pool the harder it is for the pump to catch the prime again.  The higher the pump is from the pool water level, the harder it is for the pump to catch the prime.
bulletAir Leaks - If there are any air leaks in the pool plumbing it will be more difficult to catch the prime again.  If the pump lid and O-Ring are not installed correctly or if they have cracks or are worn, it will be harder to regain the prime.
bulletPool Water Level - If the water level is low in the pool, it is harder for the pump to catch the prime.  The lower the water, the harder it is.

How to Re-Prime the Pool Pump:

  1. Turn off pool pump, pool heater and pool cleaner pump if equipped.
  2. Open Air Relief Valve on top of pool filter.
  3. Close all skimmer valves, leave main drain valve fully open.
  4. Make sure there is some water in the pump basket area.  If you are unsure then add a few gallons of water to this area of the pump.
  5. Inspect the pump lid and the O-ring for cracks or other signs of deterioration.  Lubricate the pump lid O-ring with Magic Lube or petroleum jelly and install hand tight.  Do not over tighten.
  6. Set filter valve to 'FILTER" position.
  7. Turn on pool pump.
  8. It may take a few minutes for the pump to catch the prime.  Do not let the pump run for longer than about 20-30 minutes without water circulation or overheating may occur.
  9. Once the pump has achieved circulation, slowly open one skimmer valve at a time.  Some air may enter into the pump when the valve is opened.  If it looks like the pump will loose prime, close the valve and let the pump recover from the introduction of air and slowly open the valve again.  Repeat this process until no more air enters the pump with the valve in the full open position.  Repeat for the additional skimmer valves if equipped.
  10. Close the air relief valve on the top of the filter when all air has escaped and a steady stream of water is present.
  11. If the pump is circulating normally you may turn the heater and pool cleaner pump on if desired.


These procedures apply to inground swimming pools and may vary from system to system.  Expert Pool & Spa, Inc. does not sell or service aboveground pools and these procedures do not apply to most aboveground pools.

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This website was last updated on
Tuesday May 24, 2011