MSPA spa heater runs but water heats very slowly or not to the set temperature in cold weather.

Safety first: Do not attempt to modify heater wattage or bypass safety devices.

• Improve insulation: Use an MSPA thermal ground mat and ensure the insulated cover is in good condition and used whenever the spa is not in use.
• Limit exposure: Avoid leaving the cover off for long periods in cold or windy conditions.
• Descale heater: If in a hard water area, descale the MSPA heater assembly to restore full heat transfer.
• Adjust expectations: In near‑freezing conditions, heating may take many hours. Start heating well before planned use.