Hot Tub Not Heating? Try These DIY Fixes Before Calling a Pro

Hot Tub Not Heating? Try These DIY Fixes Before Calling a Pro

Is your spa water cold? Heating issues are the number one reason customers call us. The good news is that in many cases, you can resolve the issue yourself with basic troubleshooting and a quick check of your settings.

Before you spend money on a service call, walk through these easy diagnostic steps.

Step 1: Check the Display for Errors

The first thing to do is look at your topside control panel. Is there an error message? If so, this is likely the culprit.

• Common Codes: Look for codes like FL, DY, or DR 

• Newer Models: Modern touchscreens might not use codes but will explicitly say “Heater Dry” or “Blockage Detected.”

Step 2: Troubleshooting “Flow” Errors

If you are seeing a flow error, it means water isn’t moving through the heater fast enough. Here is how to fix it:

1. Check Water Levels: Ensure your water is at the proper height. For most hot tubs, this is about an inch or two below the bottom of the headrests.

2. The “No-Filter” Test: A dirty filter is the most common cause of flow errors.

   • Power OFF the breaker to your hot tub.

   • Remove the filter (usually found under a plastic lid, grille, or basket).

   • Check the intake area for debris (rags, sponges, leaves).

   • Wait a few minutes, then power the spa back ON with the filter still removed.

   • Why do this? If the error disappears and the heater engages, you know your filter was the problem. You don’t want to pay a technician just to tell you to buy a new filter!

   • Note: If the error doesn’t return after 10–15 minutes, replace your filter.

Step 3: Clearing an Air Lock

Did you recently drain and refill the hot tub? Or did the water level drop significantly due to a leak? You may have air trapped in your circulation pump (an “air lock”).

Try these methods to clear it:

• The Power Cycle: Turn the spa off and on again. Let it run for 5–10 minutes. Repeat this several times. The startup “priming cycle” is often enough to push the air bubble out.

• The Hose Method: If cycling the power doesn’t work, take a garden hose and push water directly into the plumbing to force the air out.

  • Option A: Place the hose down the base of the filter housing (cup your hand around the hose to create a seal).

  • Option B: Locate the “heat return” port. This looks like a jet but is usually placed near the bottom of the footwell (not a seat). Hold the hose against this port to push water backward into the heater and pump.

Note: There are more advanced ways to clear an air lock by opening the cabinet, but if the methods above fail, we recommend calling a professional to avoid damaging the equipment.

Step 4: No Error Codes? Check Your Settings

If the screen looks normal but the water is cold, it is likely a settings issue.

• Check the “Heat Light”: Most tubs have an indicator (an LED, a red light, or a flame icon) that turns on when the heater is active.

  • If the light is ON but the water is cold: You likely have a mechanical failure (heater or motherboard) and need a repair technician.

  • If the light is OFF: Your spa thinks it doesn’t need to heat. Check your heating mode.

• Verify Heating Modes: Every brand is different, but you generally want your tub in “Auto” or “Ready” mode. If your tub is in “Economy,” “Sleep,” or “Rest” mode, it will only heat during filtration cycles, which may not be enough to keep the water hot. Consult your owner’s manual to adjust this setting.

Need Professional Help?

That is it! Heating problems are common but not complicated. Most heating problems that aren’t solved by this troubleshooting will require a heating element or sensor replacement. Call Prime Spa Care for additional help over the phone or to schedule an in-person service call.