Display shows FLO or FL1; heater will not turn on and spa may run pumps intermittently trying to establish flow.

Safety: Turn off power at the breaker before removing filters or opening unions. Never bypass safety switches permanently.

• Step 1 – Water level: Ensure water level is above all skimmer openings and at the recommended fill line. Low water can cause air ingestion and poor flow.
• Step 2 – Clean filters: Remove all filter cartridges. Rinse thoroughly with a garden hose from top to bottom. For heavily soiled filters, soak in a spa filter cleaner solution, then rinse. Try running the spa with filters removed for 10–15 minutes. If FLO clears, replace filters.
• Step 3 – Bleed air: With power off, slightly loosen the pump and heater unions to release trapped air until water dribbles out, then retighten. Restore power and run the pump on low speed.
• Step 4 – Check flow switch: Locate the flow or pressure switch on the heater plumbing of the Catalina control pack. Inspect wiring and connectors. With pump running, the switch should close; a technician can test continuity with a meter. If the switch does not change state with flow, replace it.
• Step 5 – Evaluate circulation pump: Listen for the circulation pump. If it hums but does not move water, or is very hot, it may be seized or failing and should be replaced.

If FLO persists after filter cleaning and air bleeding, schedule service to test the flow switch and circulation pump.