Pool Pump Will Not Prime? Start With the Water Level
A pump that will not prime is pulling air instead of water. In Arlington, through summer, the cause is usually the simplest one on the list — the water level has dropped below the skimmer mouth and the pump is drinking air. Check that before you take anything apart.
If the level is fine, you are looking for an air leak on the suction side. Here is the order a technician actually works through it.
What will not prime actually means
A pool pump is not self-priming in the way a well pump is. It needs the pot in front of the impeller full of water to get a seal and start pulling. If air keeps getting in, the impeller spins in a pocket of air and moves nothing, however healthy the motor is.
So the question is never really why will it not prime. It is where is the air coming from.
Cause 1: the water level is too low
The most common cause here by a distance, and the one people skip. A North Texas pool can lose a quarter inch a day to evaporation in July, more with wind and no cover. Once the level drops to the bottom of the skimmer mouth, the skimmer starts gulping air with every ripple.
How to check
The water should sit at roughly the middle of the skimmer opening, about halfway up the tile. If it is at or below the bottom lip, top it up with a hose, let it settle, and try priming again before you do anything else.
If topping up fixes it and it drops again within a few days, you do not have a priming problem, you have a leak. See pool leak detection for how that gets traced.
Cause 2: an air leak on the suction side
Everything between the skimmer and the impeller is under suction. Any gap there pulls air in rather than leaking water out, which is why these are easy to miss — there is no puddle to find.
How to spot it
Look at the pump lid while it runs. Water should fill the pot with no churning. A steady swirl of bubbles in the pot, or a stream of bubbles coming out of the pool returns, means air is getting in upstream of the impeller.
The usual suspects, in order
The pump lid o-ring is first every time. They dry out, flatten and crack, and Texas heat ages them fast. Take it out, check for cracks, clean the seat and the ring, and put a thin smear of silicone lubricant on it — never petroleum jelly, which degrades the rubber.
After that: the pump drain plugs, the threaded union in front of the pump, the valve stem o-rings, and finally the suction plumbing itself. A loose union is a very common find after someone has had the equipment apart.
How to find exactly where
With the pump running, work along the suction side putting a little water over each joint. When you cover the leak, the water gets drawn in and the bubbles in the pot briefly change or clear. That tells you which fitting to deal with.
Cause 3: a blocked basket or impeller
A packed skimmer basket or pump basket starves the pump, and so does debris wedged in the impeller vanes. The pump may prime slowly, prime and then lose it, or never get there.
How to check
Power off at the breaker. Empty both baskets and check the pump basket for cracks — a cracked basket lets debris through to the impeller, which is a bigger job. If you can reach the impeller, turn it by hand and feel for grit or a hard stop.
Cause 4: a valve that is not fully open
Worth thirty seconds before anything else. A skimmer or main drain valve knocked part-closed, or a multiport left between positions, will stop a pump priming and looks exactly like a failed pump. Confirm every suction valve is fully open and the multiport handle is seated firmly in Filter.
The priming sequence that works
Breaker off. Open the pump lid and fill the pot to the top with a hose. Check the o-ring is seated, then hand-tighten the lid — hand tight only, over-tightening distorts the ring and causes the leak you are trying to fix.
Open the air relief on top of the filter, switch the breaker on, and let it run. You should hear air purging and then a steady stream of water at the relief valve — close it at that point. If the pot has not filled and held within about a minute, switch off rather than letting it run dry, and go back to the air-leak hunt.
What it costs to sort out in Arlington
Most priming calls are cheap. A lid o-ring, a basket, or re-sealing a union is a small part and a short visit. It gets more involved if the suction plumbing is cracked underground or the shaft seal has failed and is letting air in at the motor.
Our service call is $149, it covers the full diagnosis, and it comes off the repair price if you go ahead. Every repair carries a one-year warranty. See pool pump repair for the detail, or equipment repair if the trouble turns out to be the filter or the valves.
Keeping it primed
Keep the water at mid-skimmer, especially July through September when evaporation is at its worst. Replace the lid o-ring yearly rather than when it fails, and lubricate it with silicone when you do. Empty the baskets before they pack solid, and replace a cracked basket the day you notice it.
Pool Pros — Family-owned pool service in Arlington, TX since 2005. Call 682-399-2593 for a free estimate.