Hayward SwimClear Air in Filter: Air Relief and Bubble Issues

Normal vs. Abnormal Air Behavior

Some air accumulation in a cartridge filter is normal and expected. When the system is first started after a service, the filter tank fills with water and air is purged through the MAR valve — this is by design. The Hayward startup procedure requires the MAR valve to be in the OPEN position when starting the pump, precisely to allow this purge.

Abnormal air behavior is when the filter never fully purges air, air is present every time you open the MAR valve even days after startup, or you see a steady stream of bubbles returning through the pool's return fittings while the pump is running at steady state.

Step-By-Step Troubleshooting

Step 1: Verify the MAR valve startup procedure was followed

Owner-level:

1. The MAR valve should be opened (counterclockwise to OPEN) before starting the pump each time the system is started after any service.
2. Close the MAR valve only when a steady stream of water — not air or a mix of air and water — discharges continuously from the valve port.
3. If you closed the MAR before the tank fully purged, reopen it briefly while the pump runs.

Tech-level: Confirm the MAR body is properly installed in the LOCK position. If the MAR was recently serviced, verify it is fully seated and locked — a partially seated MAR can allow air to re-enter the system or prevent proper pressure buildup.

Step 2: Check for suction-side air leaks

Air entering the suction side of the pump is pulled through the pump and into the filter. The Hayward manual identifies this as a cause of low water flow: "Check for air leak in intake line (indicated by bubbles returning to pool)."

Likely locations for suction-side air leaks:

• Pump lid o-ring — The most common source. Inspect for cracks, flat spots, or debris on the seating surface. A thin film of magic lube (not petroleum-based) is appropriate on the pump lid o-ring only.
• Suction union connections — The SPX3200UG gaskets at suction-side unions harden over time. Check for weeping or visible gaps.
• Skimmer connections — Cracked skimmer body, loose throat piece, or a skimmer basket lid that is not sealed.
• Low pool water level — If the water level drops below the skimmer opening, the skimmer pulls air directly. The minimum water level is mid-skimmer opening.
• Suction pipe cracks or fittings — Underground pipes can crack; fittings above ground can loosen. Check all visible suction connections.

Step 3: Isolate the air source

Tech-level procedure:

1. Open the MAR valve while the system is running and note what discharges. A brief hiss then steady water is normal. Prolonged air, intermittent air, or a mix that never fully clears to water indicates active air intrusion.
2. Watch the pump strainer lid (if clear/transparent) for air bubbles in the basket. Lots of air in the basket confirms the air is being pulled in on the suction side.
3. At the returns, hold your hand over the return fittings. A steady stream of water is normal. If you feel pulsing or see visible bubbles, suction-side air entry is confirmed.
4. Work through each suction connection systematically — pump lid, suction union, skimmer lid — looking for the source.

Step 4: Check and service the MAR valve

If the MAR valve (CCX1000V / DEX2420MAR2) is the source of air re-entry — either not seating fully after closing or leaking past its o-rings — the valve needs to be serviced.

Servicing the MAR valve:

1. Shut down the pump. Open the MAR to OPEN position. Wait for all water to stop.
2. Rotate the MAR body counterclockwise until the indicator aligns with UNLOCK. Pull straight up to remove.
3. Inspect the o-ring seals (DEX2420Z8A o-ring kit). Replace if worn, cracked, or deformed.
4. Inspect the MAR body for cracks or damage.
5. Wipe the MAR port in the upper filter body clean.
6. Reinstall: align the flange notch with the upper body notch, press straight down, rotate clockwise to LOCK. Verify discharge points away from electrical equipment.

Step 5: Verify filter installation position

The Hayward manual specifies that the filter should be positioned so it drains by gravity and the inlet and outlet plumbing connections are accessible. A filter installed significantly below pool water level, or with a complex piping layout, may trap air pockets more readily. If air problems are chronic and no suction-side leak can be found, review the overall installation position and piping layout.