Display shows “FLO” or “FLO2”; heater disabled, jets may still operate.

Safety first: Turn off power at the breaker before removing filters or opening the equipment bay.

• Remove and clean filters: Take out all filters (Tri-X or paper cartridges). Rinse thoroughly with a high-pressure nozzle from top to bottom. For heavily soiled filters, soak in a spa filter cleaner solution, then rinse and reinstall.
• Test without filters: With filters removed, restore power and run the spa. If the FLO code disappears and heat resumes, the filters were restricting flow and should be replaced if old.
• Check circulation pump operation: Look for a steady stream of water at the heater return or dedicated circulation outlet. If flow is weak or intermittent, the SilentFlo 5000/5002 circulation pump may be failing or air-locked.
• Inspect flow/pressure switch: Locate the flow switch on the heater plumbing. Ensure the wires are firmly connected and the switch body is not cracked. A stuck or failed switch can falsely signal low flow.

If cleaning filters and bleeding air do not resolve the issue, the circulation pump or flow switch likely needs replacement by a professional.