Hot tub flow error (FLO, FL1, HFL, LF, dr): is it the filter?
A flow error means the control system is not seeing enough water moving through the heater, so it turns the heater off to protect it. Every manufacturer document we checked lists a dirty or blocked filter among the first causes, along with low water, an air lock, closed valves or jets, and a pump that isn’t running or primed[26][27][12][29]. With the power off, check the water level, take the filter out and rinse or replace it, purge any air, then restore power and reset. If the error comes back with a clean filter and full water, Jacuzzi and Sundance say to call a dealer or technician[10][12].
What each code means
The code depends on who made your spa’s control system, not on the filter brand. These are the flow-related messages in the documents we checked:
| Code on the panel | Control / brand | What the manufacturer says it means | Reset, per the document |
|---|---|---|---|
| FLO | Gecko (in.ye, in.yt, in.yj, in.xe) | No water flow detected while the main pump runs[26] | Not stated; fix the cause first |
| HL | Gecko | Water in the heater reached 119 °F (48 °C) and the system stopped; Gecko says to make sure nothing is blocking flow, such as closed valves or a dirty or clogged filter[26] | Turn the spa off and on |
| HFL (M016) | Balboa | Heater flow is reduced; the heater tries again after about 1 minute[27] | Yes, it retries |
| LF (M017) | Balboa | Not enough flow, heater disabled. Balboa’s fault sheet says LF follows HFL occurring 5 times in 24 hours[27][28] | Press any button after fixing |
| dr (M028) | Balboa | Heater may be dry; spa shuts down for 15 minutes[27] | Press any button to reset |
| dry / dY (M027) | Balboa | Heater is dry and the spa is shut down; the fault sheet says this follows dr 3 times in a row[27][28] | Press any button after fixing |
| OHH (M030) | Balboa | 118 °F (47.8 °C) detected in the heater; spa shut down[27] | Press a button once water is below 108 °F |
| FL--1 “FLOW ERROR OPEN” | Sundance 780 Series | Flow switch open: the switch is faulty, the filter is excessively dirty, or there is an air lock at the circulation pump intake. The heater turns off and jets pump 1 may too[12] | Not stated; dealer if it persists |
| FL--2 “FLOW ERROR CLOSED” | Sundance 780 Series | Flow switch stuck closed[12] | Not stated; contact the dealer |
| FL--3 “FLOW ERROR TOGGLE” | Sundance 780 Series | Flow switch behaving erratically; Sundance says clean the filters and correct the water level before calling the dealer[12] | Not stated |
| E2: NO FLOW-CHECK FILTER, yellow status light | Hot Spring Highlife (2023) | No-flow / pressure-switch fault; heater off. Hot Spring says check and clean the filter, then call for service if needed[29] | The pressure switch closes once flow is restored[29] |
Jacuzzi’s filter page describes FLO and low-flow messages the same way: the system isn’t detecting enough circulation[10].
Check these in order
- Turn the power off before you open the filter compartment. Jacuzzi says this stops the pump starting unexpectedly and avoids drawing air into the plumbing[10].
- Check the water level. Sundance’s fix for FL--1 and FL--2 starts with water above all the jets but below the lowest pillow[12]. Balboa’s flow checks start with low water too[27].
- Take the filter out, rinse it and look at it. Sundance, Gecko, Hot Spring and Jacuzzi all name a dirty or clogged filter[12][26][29][10]. Jacuzzi says to inspect for damage while you rinse[10]. If it is torn, crushed or no longer recovers with cleaning, see signs your filter is bad.
- Purge any air lock. Sundance’s method: with the filter out, hold a garden hose over the filter wall fitting with a rag sealing around the hose end, run the water for 30 seconds, then reinstall the filter[12]. Gecko’s method: with the pump running, slowly loosen one pump union nut to let trapped air out, then retighten it[26].
- Open valves and jets. Gecko and Balboa list closed valves; Balboa adds too many closed jets[26][27].
- Make sure the pump that feeds the heater is running. Gecko says to confirm the main pump runs; Sundance says to cycle power at the breaker if the circulation pump isn’t running[26][12].
- Reset. Balboa LF, dr and dry need a button press after the fix[27]. Some errors need the power removed and restored[27].
Got the error right after cleaning or refilling?
That is a common pattern, and the documents point to air or water level rather than the clean filter. Hot Spring lists draining the spa without disconnecting power, and air locks in the plumbing, as causes of pressure-switch and thermal cut-off trips[29]. Sundance says that if filling through the footwell gives you an air lock, fill through the filter inlet instead[12]. On Balboa systems the spa enters Priming Mode at every power-up for 4 minutes so you can check each pump is primed, and the heater cannot run in that mode[27]. Jacuzzi also lists recurring FLO errors right after cleaning as one of the signs a cartridge needs replacing rather than cleaning[10].
Can I run the spa without the filter to see if the error clears?
The manufacturers we checked don’t recommend it. Sundance has you take the filter out only to purge air, and to reinstall it before turning the power back on[12]. Jacuzzi advises against running the spa with no filter installed, because unfiltered water carries contaminants to the pumps and heater, and suggests keeping a second clean cartridge to swap in[10].
When it isn’t the filter
- Sundance FL--2 is a flow switch stuck closed, which a clean filter won’t fix[12].
- Gecko FLO that persists: Gecko’s checklist also asks for a minimum flow of 68 L/min (18 US gal/min) and a properly plugged-in in.flo cable above the heater; if FLO still persists, it says to replace the heater and then the control system[26]. Those steps are for a technician.
- Hot Spring: call for service if the heater trips frequently[29].
- Any brand: if the spa won’t circulate or heat with a new, clean filter and balanced water, Jacuzzi says it needs professional diagnosis, and that running a faulty system can damage other parts[10].
Preventing it
A filter that is cleaned on schedule is less likely to restrict flow; see how often to clean a hot tub filter and how to clean one. If you need a replacement, search by part number, or use the model-year lookups for Hot Spring, Caldera, Jacuzzi, Sundance, Bullfrog and Master Spas.
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Questions
Can a dirty filter cause a FLO error?
Yes. Gecko’s FLO checklist includes making sure nothing is blocking the filter, Sundance names an excessively dirty filter as a cause of FL--1, and Hot Spring’s E2 message literally says “check filter”.
Why does my hot tub say FLO after I cleaned the filter?
Usually air or water level. Hot Spring lists air locks and draining without disconnecting power as causes; Sundance gives a hose method to purge an air lock at the filter fitting. Jacuzzi also lists recurring FLO errors right after cleaning as a sign the cartridge should be replaced.
How do I reset a hot tub flow error?
Fix the cause first. On Balboa systems, LF, dr and dry errors reset with any button press after the problem is resolved, and some need the power turned off and on. Gecko’s HL resets by turning the spa off and on. Hot Spring’s pressure switch resets on its own once flow returns.
Should I run my hot tub without a filter to clear the error?
No. Sundance has you reinstall the filter before turning power back on, and Jacuzzi advises against running the spa without a filter because debris can reach the pump and heater.
Will a new filter fix a flow error?
Only if the old filter was the restriction. If the error persists with a clean filter and correct water level, Jacuzzi and Sundance say to contact a dealer or technician; Sundance’s FL--2, for example, is a stuck flow switch.
Sources
- Jacuzzi: Hot Tub Filter Cleaning Made Easy
- Sundance Spas 780 Series Owner’s Manual (2024)
- Gecko Alliance: Troubleshooting Guide, Y series and in.xe (rev. 07/2023): FLO and HL messages
- Balboa Water Group: TP600 and TP400 User Guide (heater-related messages and flow-related checks)
- Balboa fault codes sheet (copy hosted by UK dealer Allswim)
- Hot Spring Highlife Collection Owner’s Manual (2023): service information and logo-light troubleshooting
This guide summarizes published manufacturer and public-health guidance; always follow your own spa’s owner’s manual. See our disclaimer.