Why is my pool pump losing prime?
Almost always because air is getting into the suction side. The usual causes are an empty or low strainer pot, a dry or poorly seated lid O-ring, a full pump or skimmer basket, a low pool water level, or a loose union or leaking valve on the suction line. Clear the basket, refill the pot, reseat the O-ring and look for bubbles at the returns.
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By Kasra Taheri, Founder, LoclisPublished
Researched and drafted with AI, then checked claim by claim against the sources listed below before it was published. Prices and rules change; the dates beside each source say when it was last checked.
Step by step
Read when to stop and call a pro, further down this page, before you start.
Step 1: Turn the pump off
Stop the pump before opening anything, and close the suction and outlet valves if your plumbing has them.[1]
Step 2: Check the pool water level
If the pool water level is low and the skimmer is starving for water, add water.[2]
Step 3: Clean the skimmer and pump baskets
Remove the strainer cover, empty the pump basket, and empty the skimmer basket, since a basket loaded with debris is a listed cause.[1]
Step 4: Inspect the lid O-ring
Wipe the cover O-ring and its groove clean, then check it and replace it if it is damaged. Lubricate it with the lubricant your pump manual names.[1]
Step 5: Refill the strainer pot
Fill the strainer housing with water up to the suction pipe level.[1]
Step 6: Refit the cover by hand
Seat the O-ring, tighten the cover knobs by hand only with no wrenches, then reopen the valves.[1]
Step 7: Restart and watch
Wait at least five seconds, switch the pump on from a safe distance, and give it up to five minutes to prime.[1]
Step 8: Look for air at the returns
Bubbles coming from the return fittings on the pool wall mean air is still entering the suction side.[1]
A pump loses prime when air gets into the suction side and the impeller can no longer pull water. Start with the cheap, common causes: the pump basket or skimmer basket is full, the pool is low, the strainer pot was not refilled, or the lid O-ring is dry or dirty. Hayward puts it plainly: any self-priming pump will not prime if there are suction air leaks.[1]
How to tell it is an air leak
Look at the returns. Leaks will result in bubbles emanating from return fittings on pool wall.[1] Other signs are air bubbles in the clear lid, a rattling or gurgling pump, and a skimmer that looks starved for water. Pentair lists the same symptoms for a filter. Low water level in pool or spa - skimmer starving for water with pump running, plus air bubbles or a low level in the hair and lint pot.[2]
The air matters beyond the pump. Pentair warns that air entering your filter can cause lid separation.[2] A pump that keeps sucking air is a reason to fix the cause, not just to keep restarting it.
The usual suspects, in the order to check them
- Low pool water level. If the water drops too low, the skimmer pulls in air. Pentair's remedy for low water level is to add water.[2]
- Full baskets. Hayward lists a strainer basket or skimmer basket loaded with debris, and the fix is to remove the cover, clean the basket and refill the housing with water.[1] After a storm or in leaf season this alone explains most "lost prime" calls.
- Empty strainer pot or poor lid seal. Hayward's fix: Make sure pump/strainer housing is filled with water and cover o-ring is clean, seated in its groove and lubricated, with the cover locked firmly in position.[1] Hayward's manual names a specific lubricant for the O-ring, so use the one your own pump manual names.
- Loose suction fittings and valves. Hayward points to loose connections on the suction side, where unions and pipe connections can be tightened, and to leaking O-rings or packing glands on valves.[1] Hayward's fix is to tighten the pipe and union connections; a persistent weep at a glued joint is a plumber's job.
- A clogged suction line. If the pump will not develop suction with clean baskets and a sealed lid, Hayward's answer for a clogged suction side is to contact a qualified repair professional.[1]
Restarting without hurting the pump
Fill the strainer housing before every restart. Running pump dry may damage seals, causing leakage, flooding, and voids warranty.[1] Tighten strainer cover knobs by hand only (no wrenches).[1] Then reopen the valves, and Wait five (5) seconds before re-starting pump.[1]
Hayward says to stand at least 10 feet from pump and/or filter when starting.[1] Priming time will depend on vertical length of suction lift and horizontal length of suction pipe, and it can take a few minutes on a pump set well above the water.[1] If pump does NOT prime within five minutes, stop motor and determine cause.[1]
Stop and call a pro if
- The pump still will not prime after clean baskets, a full pot, a sealed lid and a normal water level. The suction line may be blocked, cracked or drawing air underground.
- Water drips from the pump body or the motor end. That points to a failed shaft seal, which means opening the pump.
- The motor hums, trips the breaker or runs hot. That is an electrical or motor problem, and wiring work belongs to a licensed electrician. Virginia bars anyone from engaging in, or offering to engage in, tradesman work as defined in § 54.1-1128 without a tradesman licence, unless working under the supervision of a tradesman licensed in that specialty.[3]
- Bubbles keep streaming from the returns even though every visible connection is tight.
- The pump is old and has had several leaks. Compare repair against replacement.
Getting help in Virginia
A pump and filter service can pressure-test the suction line and replace seals. If replacement is on the table, see how much a new pool pump costs in Virginia and whether a variable-speed pump is worth it. A filter that is clogged adds strain, so also read how to clean a pool cartridge filter. You can browse pool and spa services or more pool and spa answers.
When you are ready, describe your pump problem once and local pool services quote it.
Common questions
- How long should a pool pump take to prime?
- Hayward says to wait for the pump to prime, which may take up to five minutes, and that priming time depends on the vertical length of suction lift and the horizontal length of suction pipe. If it has not primed in five minutes, stop the motor and find the cause.
- Can I just keep running the pump until it catches?
- No. Hayward warns that running a pump dry may damage the seals, causing leakage and flooding. Stop it, fill the strainer pot and look for the air leak.
- How can I tell where the air is getting in?
- Bubbles coming from the return fittings on the pool wall point to a suction-side air leak. Air in the pump's clear lid, or a skimmer that is starved of water, points to the same place.
- Why does the pump lose prime only sometimes?
- Intermittent loss usually means a basket that fills with leaves between cleanings, a pool level that drops with evaporation or splash-out, or an O-ring that seals only when it is wet and lubricated.
- Is a cracked lid a repair I can make myself?
- Replacing a damaged cover O-ring is a homeowner task, but a cracked lid is best replaced with the manufacturer's part, and a leaking shaft seal or suction pipe is work for a pool service.
Sources
- [1] Super Pump Series Owner's Manual (ISSPSERIES, Rev D), Hayward Industries. Checked October 28, 2026.
- [2] Clean & Clear Plus Cartridge Filter Installation and User's Guide, Pentair. Checked October 28, 2026.
- [3] Va. Code § 54.1-1129, Tradesman license required, Code of Virginia, Virginia General Assembly. Checked October 28, 2026.
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