Hot tub error codes: FLO, dr, OH, HL and what they mean

Common symptoms

• A short code such as FLO, dr, OH or HL alternates with the water temperature on the panel.
• A code flashes by itself and the jets, heater and lights stop.
• The panel spells out a message like “Heater Flow is Reduced” with an M number.
• The tub runs but will not heat, and a code comes and goes.
• An alarm beeps and the water feels hotter than usual.

Quick checks before anything else

• Write down the exact code before you press anything.
• Find the control maker’s name (often Balboa or Gecko) on the panel or the control box.
• Check the real water temperature with an accurate thermometer.
• Top the water up to the fill line.
• Look at the filter, and test a run with it removed.
• Open all valves and most jets.

How to read your hot tub’s display

Most US hot tubs use a control system called a spa pack, made by Balboa or Gecko. The same letters can mean different things on each, so the brand comes first. Gecko shows the code and the water temperature in turns. For its sensor messages, Balboa’s service manual says a code alternating with the temperature may be a temporary condition, while a code blinking by itself means the spa has shut down.

Newer Balboa panels spell out the problem and add a message number, such as M016 for low heater flow. Older Balboa panels show short codes like HFL, dr or OHH. Both are covered below. For inflatable spas and heat pumps, use our error code lookup.

What do hot tub error codes mean?

• Flow codes FLO, HFL, LF, and HL on Balboa: not enough water is moving through the heater.
• Dry heater codes dr and dY on Balboa: the heater may not have enough water in it to start.
• Overheat codes OH, OHS, OHH and HH, and HL on Gecko: water in the tub or heater is too hot. Stay out of the water.
• Sensor codes Sn, SnS, SnA, SnB on Balboa and Prr on Gecko: a temperature sensor is off or has failed.
• Stuck pump Stu or HOt on Balboa: a pump may be heating the water. Power down and stay out.
• Status messages ICE, Pr, Ec and SLP on Balboa are not errors; they tell you what mode the spa is in.

Step-by-step: fix the most common hot tub codes

We start with the codes you can clear yourself and end with the ones that need a technician. Most of them come down to water flow, so steps 2 to 4 fix the largest share. Our hot tub heating problems page explains how the heater and sensors work.

1. Match the code to your brand. On Gecko, HL means the water inside the heater reached 119 F. On older Balboa panels, HL is grouped with HFL as a heater flow warning. Read the table below for your brand before you act.
2. Fix flow codes (FLO, HFL, HL on Balboa, LF). Balboa’s flow checks are low water level, suction blockages, closed valves, trapped air, too many closed jets and pump prime. Gecko says to run the system with the filters taken out; if FLO clears, clean or replace the filter. Gecko also lists a minimum of 18 GPM (gallons per minute) through its heaters.
3. Bleed trapped air. After a refill, air can sit in the heater and pumps may sound odd. Gecko’s fix: start the pump, slowly loosen a union nut on the heater until air comes out, then tighten it. Balboa’s priming mode, which runs for about 4 minutes after every power-up, lets you run each pump on high to push air out.
4. Clear dry heater codes (dr, dY). Top up the water and make sure every pump is primed, meaning water flows from its jets. On Balboa, dr shuts the spa down for 15 minutes. If dr happens a third time, the panel shows dY, which you reset with a button press after fixing the cause.
5. Handle overheat codes safely. For OH, OHS, OHH, HH or Gecko’s HL, stay out of the water. Take the cover off and let the tub cool; Gecko adds cold water and shorter filter cycles in hot weather, and Balboa says to check for long pump run times and high outdoor heat. Balboa’s OHH resets with a button press only once the water is below 108 F.
6. Treat a stuck pump as an emergency. If Balboa shows Stu, HOt or “A pump appears to be stuck on,” Balboa says to power down the spa and not enter the water. A pump stuck on can heat the water to hazardous levels. Call for service.
7. Call for sensor codes. Balboa’s Sn, SnS and Sensor Balance messages mean its two sensors disagree, and SnA, SnB, SA and Sb mean a sensor failed. Gecko’s Prr is a temperature probe problem. These need a technician with a meter, although Balboa notes SA and Sb can appear briefly during an overheat.
8. Ignore status messages. ICE or IC means a possible freeze, and the pumps run on their own to protect the plumbing. Pr is Balboa’s priming mode. Ec or Ecn means Economy mode, SLP means Sleep mode, and short dashes in place of the temperature mean the reading is not current yet. None of these is a fault.
9. Reset the right way. Balboa says messages marked with a star clear with any button press, and some need the power turned off and back on. Gecko’s steps reset by turning the spa off and back on. If the same code returns, the cause is still there, so do not keep resetting it.

Balboa vs Gecko hot tub error code list

Numbers change between control models. Gecko’s in.xm2 pack, for example, shows OH above 112.5 F, and Balboa’s older OHS resets at 107 F while its current guides say below 108 F. Your spa’s own manual wins. Inflatable spas use their own codes; see our Bestway Lay-Z-Spa error codes guide.

When to call a pool or spa pro

• Any stuck-pump message (Stu, HOt, M034 or M035).
• Sensor codes: Sn, SnS, SnA, SnB, SA, Sb or Gecko’s Prr.
• A flow code that returns with full water, a clean filter, open valves and primed pumps.
• An overheat code that returns when the outdoor heat and filter cycles are normal.
• The GFCI trips when you reset the tub; see our hot tub GFCI keeps tripping guide.

If there is no code at all and the water is still cold, start with our hot tub not heating guide.

Common questions