Short answer
On the Hayward/Summit heat-pump models listed in the linked guide, FLo indicates an open water-pressure switch; low or absent flow is common, but an external controller can also display FLo when it is not calling for heat. Check the exact model, filter-pump status, and filter or bypass position. Stop if flow is confirmed but FLo persists; request qualified service.
Checks for Hayward FLO
- Match the model plate to the models covered by the Hayward/Summit guide.
- Confirm whether the filter pump is running and whether an external controller is calling for heat.
- Record the filter condition and bypass-valve position without adjusting the pressure switch.
Proof to capture before ordering parts
- Photo of the complete display and when the code appeared
- Model and serial plate, including controller revision if visible
- Filter, pump, bypass position, and pad context
Stop rule
Stop if FLo persists with confirmed flow. A qualified servicer must check the switch and controls; do not bypass the switch.
Not a diagnosis. Confirm the exact model and current manufacturer procedure before repair or parts ordering. Do not bypass safeties.
Common questions
What does Hayward FLO mean on a guide-listed heat pump?
FLO indicates the water-pressure switch is open on the models covered by the linked Hayward/Summit guide.
What should I check first for FLO?
Match the model plate to the models covered by the Hayward/Summit guide. Confirm whether the filter pump is running and whether an external controller is calling for heat. Record the filter condition and bypass-valve position without adjusting the pressure switch.
When should I stop checking FLO?
Stop if FLo persists with confirmed flow. A qualified servicer must check the switch and controls; do not bypass the switch.
Related codes
Manufacturer source
Hayward/Summit Heat Pump Troubleshooting Guide (PDF). Last reviewed: . Consult the guide's model list before using these checks.
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