Balboa Hot Tub FLO Error — No Flow Detected Fix

What Does This Error Mean?

FLO means the flow switch detects no water flowing through the heater — the system shuts off heat to prevent damage.
Most often it's a clogged filter, low water level, closed valve, or air-locked pump.
Check water level first (above the filter line), pull and rinse the filter cartridge, and confirm all valves are open.
FLO usually clears once flow is restored.

Affected Models

Balboa BP series control packs
Balboa GS series
Balboa GL series
Balboa M7 spa packs

Common Causes

Filter cartridge clogged with dirt or debris
Water level below the skimmer intake
Closed or partially closed valve in the plumbing
Pump air-locked after recent water change
Flow switch itself failed (rare)

How to Fix It

Check the water level.

Open the spa cover.
Look at the water level — should be above the highest skimmer intake but below the headrests.
If low, fill with a garden hose to the proper level.
Low water = no flow = FLO error.
Most common cause for FLO.
Pull and rinse the filter cartridge.

Open the filter compartment.
Pull the filter cartridge out (twist counterclockwise or lift, depending on model).
Rinse with a garden hose, working from the inside out to flush debris.
For heavy buildup, soak overnight in filter cleaner solution.
Reinstall.
Check that all valves are open.

Walk around the equipment area (usually behind a panel near the corner).
Look at the valves on the plumbing — should all be in the OPEN position (handle parallel to the pipe).
Closed or partially closed valves are common after service or accidental bumps.
Bleed the pump if air-locked.

If you recently drained and refilled the spa, air can be trapped in the pump.
Loosen the pump union slightly until water trickles out (catch with a towel), then retighten.
This bleeds air.
Try restarting the spa — pump should prime and water should flow.
Reset and test.

Turn the spa off at the breaker for 30 seconds.
Restore power.
The pump should prime and run.
Wait 1-2 minutes — FLO should clear once water flows past the switch.
If FLO persists, the flow switch itself may have failed (50–100 USD part).

Frequently Asked Questions

Why does FLO appear seasonally?

In summer, leaves and debris fall into the spa, clogging filters faster.
In winter, freezing can block plumbing or damage flow switches.
If FLO appears with the seasons, address the cause — leaf cover for summer, freeze protection for winter.

Will the spa heat with FLO showing?

No — Balboa control packs disable the heater when FLO is active.
This protects the heater from running dry and damaging the heating element.
The pump may still circulate (depending on cause), but no heating.
Fix the flow issue and FLO clears, then heating resumes.