How to Fix a Hot Tub Flow Error (FLO, FL1 and Low Flow)
A flow message means the heater needs more water.
Check six things in order. Your tub has paused its heater because not enough water is passing through it.14 Most of the time the fix takes a few minutes and no tools: top up the water, clean the filter, clear the suction, open the valves and let the pump clear its air. The chart below puts the checks in order.
What a hot tub flow message means
The heater is a small chamber with a hot element in it, and the water passing through carries the heat away. When the control cannot see enough water going through, it pauses the heater to protect it.14 That is why the first checks are all about moving water.
The wording depends on the make of your control. Balboa panels show messages such as FLO, HFL and LF, or a line such as the water flow is low. Gecko panels show codes such as FLO and FL1.3 Whichever you see, the same first checks apply, and your manual lists the exact meaning for your tub.15
The six-check flow chart
Start at check 1. If the answer is Yes, move on to the next check. If it is No, do the fix beside it, then carry on down.
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1
Is the water at the right level?
The level mark is in your manual. Low water is one of the most common causes of a flow message,4 and tubs with a water level sensor switch the pump and heater off when it drops.1
If no
Top up with a hose.
Fill to the level in your manual, then carry on down the chart.
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2
Is the filter clean?
A dirty or collapsed cartridge restricts the water reaching the pump.4
If no
Rinse it or soak it overnight.
Isolate the power as your manual describes, lift the cartridge out and rinse it. A cartridge cleaner soak lifts oils and scale, and a worn cartridge is best replaced.
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3
Is anything blocking the suction?
The skimmer and suction fittings need a clear path into the pump.14
If no
Clear leaves, hair and debris.
Remove anything sitting over the skimmer or suction fittings and empty the skimmer basket.
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4
Are the valves and jets open?
Closed valves and too many closed jets both cut the flow.1
If no
Open them fully.
Turn each diverter valve and jet adjuster to fully open.
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5
Has the pump cleared its air?
Air gets trapped after a drain and refill and stops the pump moving water.14
If no
Prime the pump.
Run the jets so the air can escape. On a Balboa system, priming mode lasts less than five minutes and you press the Jets button repeatedly during it.2
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6
Reset once. Has the message gone?
Put the cause right first, then clear the message the way your manual describes. Resetting before the fix brings the same message back.4
If yes
Back to soaking.
The heater restarts and the water warms back up to your set temperature.
If no
Call your dealer or a service engineer.
The pressure switch, pump and heater are theirs to check, and the control box has no user-serviceable parts.2
Cleaning the filter
A clean cartridge keeps water moving freely, and it is the check you can easily keep ahead of. Rinse the cartridge regularly and give it an overnight soak when it looks greasy or scaled. Our beginners guide to hot tub maintenance sets out a simple routine.
If the cartridge has done its time, browse our hot tub and swim spa filters, or look through hot tub parts and spares.
AquaSPArkle Immerse Hot Tub Filter Cartridge Cleaner Aqua Sachet£3.99
A soluble sachet for an overnight clean that removes dirt, grease, scale, rust and oils, with no mess to measure out.
If the message comes back
What the tub is doing
Some controls count how often the message appears. A Balboa 300F system shows a persistent low-flow message on the fifth occurrence within 24 hours. The heater then stays off while the pump, jets and lights carry on as normal, and you press a button to reset once the cause is fixed.2
What to do next
Pressure-switch codes such as Gecko FLO, FLC and FL2 point to the switch itself, which is a job for a technician.3 Your dealer or a service engineer can check the switch, pump and heater, and our guide to common hot tub problems and solutions covers other faults you may meet.
Quick answers
Open a question to read the answer.
What does a flow error mean on a hot tub?
The control has found less water moving through the heater than it expects, so it pauses the heater to protect it. The usual reasons are low water, a dirty filter, a blocked suction, a closed valve or air in the pump.
How do I reset a hot tub flow error?
Put the cause right first, then clear the message the way your manual describes. On many panels that is a single button press. Resetting before the fix tends to bring the same message straight back.
Why does my hot tub show a flow error after refilling?
Refilling can leave air in the pump and pipework. Top the water up to the level in your manual, then run the pump in priming mode and press the Jets button repeatedly until the air clears.
How long before the heater tries again?
It depends on the control. On Balboa systems the heater restarts after about a minute following a low-flow message, and a possible dry-heater message pauses the tub for 15 minutes before it resets.
Can I use the hot tub while it shows a flow message?
The heater is paused, so the water will slowly cool. Many tubs keep the pump, jets and lights running, but it is best to put the cause right and clear the message before your next soak.
When should I call a hot tub engineer?
Call your dealer or a service engineer if the message returns after the six checks, if the pump runs but no water moves, or if your manual points to the flow or pressure switch. The control box has no user-serviceable parts.
Sources
- Balboa Water Group, spa touch 3 user guide, View messages (flow-related checks), updated 30 October 2024
- Balboa Instruments, 300F-Series Operation Guide, diagnostic messages and priming mode, 8 November 2007
- iFixit, Hot Tub Error Codes (Balboa and Gecko flow codes)
- Bath and Spa Parts, Balboa topside panel error codes troubleshooting guide
- Leslie's, Spa and hot tub error codes: FL, FLO, FLOW, LF
Paul Margerison
Managing Director & Founder, Outdoor Living
A flow message is your tub looking after its own heater. This guide puts the checks in the order that gets you back in the water fastest.