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Fix a hot tub that will not heat

We'll confirm the pump is circulating, rule out power and flow, then isolate the cause—heater, flow switch, or high-limit—or tell you when to call a pro.

Troubleshooting · Home appliances
20–45 min
What you'll need
  • Multimeter (for continuity tests on the heating element)
  • Owner's manual (for error codes, flow switch location, heater access)
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Steps

Goal: Confirm circulation, rule out power and flow, then isolate the heating fault.

  • Check that the hot tub pump is running and water is flowing through the jets.
  • Good: The pump is running and water is circulating. Proceed to Check circulation and power.
  • Bad: The pump is off or there is no flow—start the pump and check for air locks or blockages. See When to get help.

Check circulation and power

Goal: Rule out pump and power before testing the heater.

  • Verify the pump is running and water is moving through the jets. Check the circuit breaker and GFCI—press reset if tripped.
  • Check the control panel for error codes. Note any codes and look them up in your owner’s manual. A power cycle (off 30 seconds, then on) may clear transient errors.
  • Good: Pump running, power on, and no error codes. Proceed to Heating path.
  • Bad: Pump will not run, GFCI trips immediately, or persistent error codes—call a pro.

Heating path

Goal: Test the flow switch, high-limit, and heating element.

  • Check the flow switch per your owner’s manual. It must close when the pump runs. Do not bypass it.
  • Check the high-limit switch. If tripped, let the water cool and reset per your owner’s manual.
  • Shut off power at the breaker. Locate the heater and test the heating element for continuity with a multimeter. No continuity means the element has failed—replace it or call a pro.
  • Good: Flow switch works, high-limit is reset, and the heating element has continuity. The tub should heat.
  • Bad: Flow switch stuck, high-limit trips repeatedly, or heating element has no continuity—replace parts or call a technician.

When to get help

Call a hot tub or spa technician if:

  • The heating element tests bad and you are not comfortable replacing it.
  • The control board shows persistent error codes you cannot resolve.
  • The GFCI trips immediately when reset.
  • You have checked circulation and power and the tub still does not heat.

Electrical work near water requires care. Confirm when to escalate: bad heater element, control board faults, or repeated high-limit trips.

Verification

  • The pump is running and water is flowing through the jets.
  • The heater fires and the water temperature rises toward the setpoint.
  • No error codes, no GFCI trips, and the high-limit has not tripped.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm circulation Verify the pump is running and water is flowing through the jets.
  2. Power and GFCI Check circuit breaker and GFCI; both can prevent heat.
  3. Flow switch and high-limit Check flow switch closes when pump runs; reset high-limit if tripped.
  4. Heating element Test heating element for continuity; replace if failed.
  5. Call a pro Bad heater element, control board faults, GFCI trips immediately—call a hot tub technician.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Whether the pump is running
  • GFCI and circuit breaker status
  • Error codes (if any)
  • Flow switch / heating element test results
  • Steps already tried

Is the pump running and water circulating?

Hot tub heaters require water flow to operate. No flow means the heater will not fire.

Check that the pump is on and water is moving through the jets. Good: pump running and flow visible—proceed to power check. Bad: pump off or no flow—start the pump, check for air locks or blockages, then retest.

Yes No

You can change your answer later.

Is power on and GFCI reset?

Circuit breaker and GFCI can prevent heat. Hot tubs use GFCI protection.

Verify the circuit breaker has not tripped. Check the GFCI—press reset if tripped. Good: power on and GFCI reset. Bad: breaker tripped or GFCI trips immediately—fix power first or call a pro. GFCI that trips on reset indicates a fault.

Yes No

You can change your answer later.

Does the flow switch close when the pump runs?

The flow switch must detect flow for the heater to fire.

Check the flow switch per your owner's manual. If the pump is running but the heater does not fire, the flow switch may be stuck or faulty. Good: flow switch closes when pump runs. Bad: flow switch stuck or failed—replace or call a pro. Do not bypass the flow switch.

Yes No

You can change your answer later.

Does the heating element have continuity?

The heating element is inside the heater assembly. Test with a multimeter. Shut off power first.

Shut off power at the breaker. Locate the heater per your owner's manual. Test the heating element for continuity. No continuity: element failed—replace or call a pro. Continuity: check the high-limit switch—it may have tripped. Reset if needed. If all tests good but still no heat, call a technician.

Yes (good) No (failed)

You can change your answer later.

Is the high-limit switch reset?

The high-limit trips when water is too hot. It resets when the water cools.

Check the high-limit switch. If tripped, let the water cool and reset per your owner's manual. Good: high-limit reset, heater fires. Bad: high-limit trips repeatedly—thermostat or heater faulty; call a pro.

Done

Replace heating element or call a pro

Replace the heating element with a matching part per your owner's manual, or call a hot tub technician. Heating element replacement may require draining and plumbing work on some models.

Done

Call a technician

Call a hot tub or spa technician if: pump will not run; GFCI trips immediately; flow switch is stuck and you cannot replace it; heating element tests bad and you are not comfortable replacing it; or control board shows persistent error codes. Electrical work near water requires care.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a hot tub run but not heat?
Common causes: pump not circulating (no flow), tripped circuit breaker or GFCI, failed heating element, stuck flow switch, or tripped high-limit switch. Check circulation and power first, then the heater and flow switch.
Can I fix a hot tub that will not heat myself?
Yes, for basic checks: confirm pump is running, check circuit breaker and GFCI, inspect the flow switch. Replacing the heating element is DIY on some models if you are comfortable with electrical work. Complex control board or plumbing issues require a pro.
When should I call a technician for a hot tub that will not heat?
Call a hot tub or spa technician if the heater element tests bad and you are not comfortable replacing it, if the control board shows error codes you cannot resolve, or if you have checked circulation and power and the tub still does not heat. Electrical work near water requires care.

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