Display shows OH or OHH and the spa shuts down; water may feel excessively hot near the heater outlet.

Safety: Overheat conditions can be dangerous. Turn off power at the GFCI immediately and allow the spa to cool with the cover open.

• Remove cover and cool down: Open the spa cover to allow heat to escape. Do not use the spa until the OH code is resolved.
• Check water level and filters: Verify proper water level. Remove and clean the filter cartridge thoroughly. Run the spa without the filter once it has cooled to see if the OH code returns.
• Inspect circulation: With power restored and water cooled, confirm that the circulation pump is running whenever the heater icon is on. Look for strong water movement at the heater return or dedicated circulation jet.
• Sensor inspection: Turn power OFF and locate the high-limit sensor (usually a thermistor inserted into a dry well on the heater tube or attached to the heater housing). Ensure it is fully seated and its wiring is intact.
• Check for stuck heater: If the heater continues to warm the water even when the control panel shows no heat demand, the heater relay on the control board may be stuck closed. This is a serious fault and requires immediate professional service.
• Call a technician: If OH persists after restoring proper flow and cleaning filters, have a Hydropool technician test the high-limit sensor and control pack. Do not bypass safety sensors.