Troubleshooting guide
Hot tub overheating
If the topside shows an overheat code or the water feels too hot, stay out of the water. The control has shut things down to protect you. Here's what it means and what to check.
Stay out of the water
What the codes mean
| Brand / code | What the manufacturer says |
|---|---|
| Balboa OHS (M029, "water is too hot") | Spa water reached 110°F and spa functions are disabled. Auto-resets when water drops below 108°F. Check for extended pump operation or high outdoor temperatures. |
| Balboa OHH (M030, "heater is too hot") | A sensor detected 118°F in the heater and the spa shut down. Reset when the water is below 108°F, then work through the flow-related checks. |
| Gecko OH | Spa water reached 108°F. Do not enter the water. |
| Gecko HL | Water in the heater reached 119°F and the system stopped. Do not enter the water. |
Safe things to try
- Confirm with a thermometer. Gecko's guide starts every overheat case by comparing a digital thermometer reading with the topside.
- Hot weather? Gecko suggests taking the cover off to let it cool, adding cold water and shortening filtration cycles. Balboa points to long pump run times and hot weather.
- Check flow. Heater-overheat codes often come from poor flow: dirty filter, closed valves, low water. Clean the filter and check the water level.
- Pump won't turn off? If a pump keeps running when everything is off (outside a filter cycle), that's a control problem. Power the spa down and call for service.
When it's a tech job
Repeated overheat codes with normal flow usually point to a sensor, a stuck relay in the control pack or a pump that won't shut off. A tech can confirm on video using the topside message and a thermometer reading, then tell you what part you need.
Common questions
What does OH mean on a hot tub?
On Gecko controls, OH means the spa water reached 108°F; on Balboa systems, OHH means the heater reached 118°F and OHS means the spa water reached 110°F. Stay out of the water, let it cool, and check flow and the filter.
How hot is too hot for a hot tub?
The U.S. Consumer Product Safety Commission says hot tub water should never exceed 104°F, and the CDC gives the same limit. Check the temperature with an accurate thermometer, because built-in thermostats can be off.
Why does my hot tub overheat in summer?
Long filter cycles and pump run times add heat, and hot weather keeps it from cooling. Manufacturers suggest shortening filtration cycles, opening the cover to cool it and checking for a pump that won't shut off.
Related guides
Safe hot tub temperature
104°F is the ceiling. Why, and who should go lower.
Read the guideBalboa error codes
HFL, LF, dr, OHH, OHS, sensor and GFCI messages, from Balboa's own guides.
Read the guideGecko error codes
FLO, HL, OH, Prr, AOH and UPL, from Gecko's troubleshooting guide.
Read the guideHot tub not heating
Jets run but the water stays cold. Usually it's flow, not the heater.
Read the guideSources
- Balboa Water Group, Spa Touch 3 user guide: panel messages, flow-related checks and reminders
- Balboa Water Group, TP500S / TP600 system user guide (42339 rev A1): priming mode, freeze protection, GFCI trip test and message codes
- Gecko Alliance, Y-series and in.xe troubleshooting guide (9919-101313-D, rev. July 2023): FLO, HL, OH, Prr, AOH and UPL messages
- U.S. Consumer Product Safety Commission: CPSC warns of hot tub temperatures (release 79-071)
Brand names belong to their owners. Hot Tub Helpline isn't affiliated with or endorsed by any manufacturer. Steps and codes vary by model and year, so always check your own owner's manual.