Symptoms
- Water stays lukewarm or cold despite the heater setting
- Control panel shows an error code related to flow or heat
- Jets work fine but temperature doesn't rise
Likely causes
- CommonDirty filter restricting water flow to the heaterHeaters have safety sensors that won't fire if flow is too low.
- CommonTripped GFCI breaker or partial power lossHot tubs are on dedicated GFCI circuits that can trip without other symptoms.
- PossibleAir lock in the plumbing preventing proper circulationTrapped air can mimic a flow problem and block heating.
- PossibleFailed heater element or high-limit sensorThe heating element itself can burn out over years of use.
What to do
- Check the control panel for any flow or heater error codes and note them.
- Remove and clean the filter cartridge thoroughly, since a clogged filter is the most common cause of flow-related heating issues.
- Check the breaker panel and reset the GFCI breaker dedicated to the hot tub if tripped.
- Bleed any air lock by loosening a union fitting slightly on the pump until water flows steadily, then retighten.
- Confirm the water level is above the skimmer/intake, since low water can also disrupt flow.
- If flow is confirmed good and the heater still won't fire, the heating element or sensor likely needs professional replacement.
Tools and parts
- Filter cleaning supplies
- Wrench (for unions)
Hot tub filter cartridgeSearch: “hot tub replacement filter cartridge”
Hot tub heater elementSearch: “hot tub heater element replacement”
When to call a pro
A hot tub technician should handle heater element replacement or any diagnosis involving the circuit board.
Safety
Use caution
Never open the equipment cabinet or work on electrical components while the hot tub is powered; shut off the breaker first.