Control panel displays FLO and spa will not heat; circulation pump may or may not be running.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power at the spa’s GFCI breaker before opening any equipment bay or removing filters. Never run the spa without water covering all suctions.
- Check water level: Ensure water is at least halfway up the skimmer opening. Top off if low, then reset power and see if FLO clears.
- Clean or bypass filters: Remove the filter cartridges from the filter well. Rinse thoroughly with a garden hose from top to bottom. For testing, run the spa briefly with filters removed. If FLO disappears, replace or deep-clean the filters.
- Bleed air from circulation pump: With power OFF, open the equipment bay. Locate the small circulation pump (often connected directly to the heater tube). Loosen the pump’s bleed screw or union slightly until water seeps out and air stops, then retighten. Restore power and check for normal flow.
- Inspect suction and skimmer: Remove any debris from skimmer basket and suction covers. Make sure all slice valves on either side of the circulation pump are fully open.
- Test flow/pressure switch: With power OFF, locate the flow or pressure switch on the heater manifold. Check that its wires are firmly connected. If FLO persists after filter cleaning and bleeding air, the switch may be stuck open and require replacement.
If the FLO error returns immediately after reset and you have good water level and clean filters, schedule a technician to test the circulation pump amperage and replace the flow switch or pump as needed.