Display shows OH or OHH, spa shuts down, pumps may run briefly then stop, water feels excessively hot near heater outlet.

Safety first: Turn off power at the GFCI breaker and allow the spa water to cool to below 100°F (38°C) before further troubleshooting.

• Remove cover and ventilate: Open or remove the spa cover to allow heat to escape. In hot weather, provide shade if possible.
• Check filters and water level: Ensure water level is correct and filters are clean. Dirty filters can cause localized overheating at the heater.
• Inspect circulation: With power restored after cooling, verify that the Clearwater Spas circulation pump or low-speed pump is moving water through the heater (you should see flow at the heater return).
• Check for closed valves: Confirm that all slice valves around the pump and heater are fully open.
• Sensor check: If OH appears immediately on power-up with cool water, the temperature sensor or high-limit sensor may be faulty and sending incorrect readings.

If the spa overheats repeatedly or trips OH quickly, discontinue use and have a technician test the temperature sensors and heater relay on the control board.