Hot Tub Fault Codes: What They Mean & What to Check

A hot tub FLO error usually means the system has detected insufficient water flow through the heating or circulation system.

Things you can check:

Start by checking the water level and make sure there is nothing obstructing the skimmer or suction points. A dirty or clogged filter is another very common cause.

You can remove the filter temporarily and restart the spa in accordance with the manufacturer's instructions. If the fault disappears, the filter may need a thorough clean or replacement.

If the warning remains, possible causes include an airlock, circulation pump problem, flow sensor, pressure switch or restriction within the pipework.

If you are unsure, switch the spa off and arrange for the hot tub circulation system to be professionally checked.

The control system believes there is not enough water passing through the heater.

Operating a heater without sufficient water flow can cause damage, so the hot tub may automatically shut the heater down to protect the system.

Things you can check:

• The hot tub has the correct water level
• The filters are clean
• Water can move freely through the circulation system
• Isolation valves are fully open
• Jets have not all been closed
• The circulation or heating pump is running

Air trapped in the plumbing after draining and refilling a hot tub can also trigger a heater dry warning.

If the warning continues, the hot tub should be professionally inspected before further use.

The control system has detected an unusually high water or heater temperature.

What to do:

Do not use the hot tub while an over-temperature warning is displayed.

Remove the cover and allow the water to cool naturally. Check that there is adequate water circulation and that the filters and suction points are not blocked.

High outside temperatures, long filtration cycles, restricted water flow or a problem with the heater, pump or temperature sensors can all contribute to overheating.

If the warning returns after the hot tub has cooled, arrange for the system to be professionally checked.

The control system is receiving an incorrect or inconsistent reading from one or more temperature sensors.

What to do:

Try switching the hot tub off safely at the isolator, wait briefly and restart it.

If the sensor warning returns, professional diagnosis is recommended. The problem may involve a temperature sensor, wiring, connection or the hot tub's main control system.

Sensor testing generally requires specialist equipment and is not something we recommend attempting yourself. Unicorn provides hot tub fault finding and repair services for problems that require further investigation.

Some Gecko and other hot tub control systems display an FLC warning when they detect a problem with the flow sensing system.

Things you can check:

Check that the water level is correct, the filter is clean and water appears to be circulating normally.

If everything looks normal but the warning continues, the flow sensor, pressure switch, wiring or control system may need further testing.

This is often a protection message rather than a component failure. The hot tub has detected temperatures low enough for freezing to become a risk.

The control system may automatically operate pumps and other equipment to keep water moving and help protect the plumbing.

What to do:

Do not switch the spa off unnecessarily during freezing weather.

Check that the hot tub has power and that the water level is correct. If the pumps are not operating or the spa cannot maintain temperature, arrange a repair promptly to reduce the risk of frozen pipework.