Control panel displays OH and spa shuts down; water in the tub feels extremely hot, often above the set temperature.

Safety first: Turn off power at the GFCI breaker before touching any components. Extremely hot water can cause burns—do not enter the spa until temperature is safe.

• Step 1 – Remove spa cover and let it cool: Open the Tuff Spas cover and allow the water to cool naturally. Do not add cold water rapidly to a very hot tub to avoid shell stress.
• Step 2 – Check water level: Ensure water level is above all jets and at the recommended fill line. Low water can reduce flow and cause overheating.
• Step 3 – Clean or replace filter: Remove the Tuff Spas filter cartridge from the filter well. Rinse thoroughly with a garden hose from top to bottom. If the cartridge is more than 1–2 years old or heavily stained, replace it.
• Step 4 – Restore power and reset: After water cools below 104°F (40°C), turn the GFCI breaker back on. Many Tuff Spas packs will clear OH automatically once temperature is normal; if not, power-cycle the spa for 30 seconds.
• Step 5 – Check for stuck heater relay: If the spa continues to heat past the set temperature, the heater relay on the control board may be stuck closed. This requires testing with a multimeter and typically replacement of the control pack or heater relay board by a qualified technician.

If OH returns quickly after cleaning the filter and confirming proper water level, contact a spa technician to test the high-limit sensor and control board.