Hayward Super Pump VS 700 Won't Prime: Diagnosing Suction Air Leaks and Flow Problems

How Self-Priming Works on the Super Pump

The Super Pump is a centrifugal pump with a volute designed to trap enough water to begin impeller action on startup. When the impeller spins in the priming water, it creates a partial vacuum that draws air from the suction pipe and replaces it with pool water. This process — called self-priming — can take up to ten minutes depending on the vertical lift and horizontal run of the suction line.

The critical constraint is that the impeller must always be surrounded by water. A pump running dry — even for 30 seconds — can score the ceramic shaft seal surfaces and cause permanent seal failure. The Hayward manual explicitly warns: never operate the pump without water. If you arrive at a site and the strainer housing is dry, fill it before attempting a restart.

On two-speed models, the pump is self-priming only on high speed. Running on low speed during a priming attempt will almost never succeed — the reduced impeller velocity cannot generate enough vacuum to draw water from depth.

Step 1: Fill the Strainer Housing and Check the Cover O-Ring

This is the starting point for every priming failure diagnosis. Skipping it is the most common diagnostic mistake.

1. Turn off the pump at the breaker.
2. Close the suction and return valves to prevent water from draining back while you work.
3. Open the filter's manual air relief valve to release any system pressure.
4. Turn the strainer cover hand knobs counterclockwise and remove the cover. Never use a wrench on the hand knobs — they are designed for hand tightening only.
5. Remove and inspect the strainer basket. If it is full of debris, the restricted flow may have caused the priming failure. Clean the basket thoroughly.
6. Inspect the strainer cover o-ring. Look for: flattening (permanent deformation from compression), cracking, debris embedded in the sealing surface, or a dry, brittle texture.
7. Clean the o-ring groove in the strainer housing. Any grit or debris in the groove will prevent a seal.
8. Lubricate the o-ring with Jack's 327. This is the manufacturer-specified lubricant — petroleum-based greases can swell rubber o-rings over time.
9. Fill the strainer housing completely with water — all the way to the top of the housing, not just partially.
10. Reinstall the clean, lubricated o-ring, then install the strainer cover. Tighten the hand knobs by hand only — snug but not forced.

Step 2: Check for Suction-Side Air Leaks

Any opening in the suction piping between the pool and the pump will prevent the pump from building vacuum. The most reliable indicator of a suction air leak is air bubbles issuing from the return fittings in the pool wall while the pump is running.

1. Start the pump and watch the return jets in the pool. Fine bubbles or pulsing water flow indicates an air leak somewhere on the suction side.
2. Inspect every union and threaded connection between the skimmer and the pump inlet. Look for: visible gaps, cracked fittings, loose union nuts, or missing PTFE tape on threaded joints.
3. Check all gate valves and ball valves on the suction line. The packing glands around valve stems are a common source of slow air leaks that are hard to see but can prevent priming.
4. Check any flexible hose sections for holes, kinks, or loose clamps.
5. If bubbles are present and you cannot find the leak visually, listen for a hissing sound at each fitting while the pump is running. You can also run your hand slowly along the suction pipe to feel for cool air movement.

Step 3: Check the Skimmer Basket and Water Level

A skimmer basket packed with leaves and debris can create enough restriction that the pump cannot pull adequate water — effectively the same result as a closed valve. Pool water level matters too: if the water drops below the skimmer throat, the skimmer draws air rather than water.

1. Remove the skimmer lid and pull the skimmer basket. Clean it completely.
2. Check the pool water level. It should be at approximately mid-skimmer opening. If the level is low, the pump will draw air through the skimmer regardless of basket condition.
3. With a full skimmer basket removed and the pump running, check whether suction is present at the bottom skimmer port. If you feel no pull, suspect a blocked suction line or a valve issue.

Step 4: Test for Suction Line Blockage

If the strainer housing is full, the o-ring is good, there are no visible air leaks, and the baskets are clean, but the pump still won't prime, the next suspect is a blocked or restricted suction line.

1. With the pump running, observe the suction gauge or vacuum gauge at the pump strainer (if installed). A vacuum of 5–6 inches Hg or greater indicates the pump is developing suction — the problem is then in the suction piping or a blocked drain port.
2. If no vacuum gauge is available, remove the skimmer basket and cover the bottom suction port firmly with your hand for about 5 seconds with the pump running. You should feel strong suction pulling against your hand. No suction means the pump is not developing vacuum.
3. If the pump develops vacuum but no water flows, the suction line is blocked. Common locations: the main drain, a partially closed valve, or debris lodged in the suction pipe.
4. If the pump does not develop vacuum despite a sealed, water-filled strainer and no air leaks, suspect a motor rotating at low RPM (low voltage) or a damaged impeller that cannot generate suction.

Step 5: Check Impeller Condition

A cracked, worn, or debris-clogged impeller cannot generate adequate vacuum for priming. Impeller problems are less common than air leaks but should be considered when all other causes have been eliminated.

1. Turn off power at the breaker.
2. Remove the four 3/8" x 2" housing cap screws. Slide the motor assembly out of the strainer housing.
3. Pull the diffuser off the seal plate. Inspect the impeller vanes for: debris packed between vanes, cracked or missing vanes, or visible corrosion.
4. Clear any debris from the impeller passages. If vanes are cracked or the impeller shows heavy wear, replace it using the correct part for your model (see the parts listing in the manual).
5. Reassemble in reverse order. Fill the strainer housing before restarting — do not restart with a dry strainer after a wet end service.