Spa heats very slowly or cannot reach set temperature in cold weather

Safety first: Ensure GFCI protection is functional; no internal electrical work is required for basic checks.

Slow heating can be due to both heater performance and heat loss.

• Verify mode and setpoint: Confirm the spa is in Standard/Ready mode and the set temperature is correct.
• Inspect cover: Check the American Whirlpool cover for heavy waterlogging, tears, or poor seal. Replace if it no longer insulates well.
• Check for air leaks: Inspect cabinet panels and equipment bay for gaps where warm air escapes; reseal or insulate as needed.
• Descale heater (if accessible): If you have hard water and an accessible heater, have a technician inspect for scale buildup that reduces efficiency.

If the spa never reaches temperature even in mild weather, the heater output or control logic should be tested by a professional.