Spa Not Heating Water: Causes and Fixes

A spa is enjoyed best when the water is hot or at least warm. That’s when the massage function works best and has the most benefits to your body. When your home or commercial spa doesn’t heat the water or even keep the heat at a certain temperature, it’s a major letdown. Luckily, we have the solution for you. 

Replace the faulty thermostat, circuit breaker, fuses, heater contactor, heating element, burnt wires and reset a tripped Hi-limit switch to make your spa heat again. Besides that, make sure your spa has heating capabilities and is properly insulated to heat and preserve the heat respectively.

For a home foot spa, the problem is usually a weak heating element or poor insulation. Knowing how to clean your home foot spa helps in preventing some of these problems. If you’re unable to perform the repairs yourself, you’re better off calling for an expert on the issue. The good news is, the most common causes to a spa not heating are usually the easiest to fix. 

Spa Not Heating Water

What Causes a Spa Not to Heat Water?

If you have one of the best foot spas for home use, you don’t need to return it to the vendor or throw it away in frustration when it won’t heat water. Instead, look for the causes and solutions below.

The reasons include the following:

1. The Spa Has No Heating Capacity 

When buying your spa, ensure that it’s clearly stated to have a heating element and other details about it. At times, the spa may only be capable of keeping water warm for a certain period of time but still requires you to add in it warm water heated elsewhere. 

Most foot spas aren’t equipped with heating elements strong enough to heat the water to a certain temperature as you may expect. Instead, they have weak heating elements simply meant to keep the temperature to a certain level for about 15 minutes or thereabouts. 


Ensure that the spa you’re buying can heat water and keep it at that temperature. The best way to do this is to read about the foot spa (or other spa) on the manufacturer’s site and even check on user forums.

2. Poor Insulation

Part of the reason spas keep water within a given temperature is the high level of insulation they have. This prevents the loss of heat from the warm water to the environment. The other reason is the heating element which should keep heating the water while in use. 

When the insulation has been compromised, it’s hard getting the spa to maintain the temperature of the water for the period you’ll be using the spa. 


Know the material the spa is made of beforehand. Thin plastic isn’t good at keeping heat and so does thin metal. Go for thick insulation whether it’s metal, plastic, acrylic or other material. 

3. Tripping Hi-Limit Switch

The purpose of a Hi-Limit switch in your spa is to cut off the current when the water gets too hot or there’s a current surge. This is a good thing given that it helps prevent damage to the rest of the spa or water getting too hot that it scalds you. It’s basically a circuit breaker. 

When this switch senses higher than normal temperature whether correctly or erroneously, it’ll trip to save your skin. At times, the tripping could be in error due to various reasons such as:

  • A restricted flow of water due to clogging.
  • Too much temperature.


Reset a tripped Hi-limit switch by pressing the red button on it. Different spa models have these switches in different shapes and locations. The manual to your spa will show you where it’s located and how to reset it. 

4. Poor Heating Element

The heating element is what provides heat to the water in the spa. If it’s not working properly, you’re bound to have inconsistent heating or no heating at all. 

For small home spas, the heating element is located under the water bowl and you simply need to flip the spa over, release the screws then look for it among the electronics. Again, different spas will have different types of electronics and arrangements hence the need to read from the manual to find yours. 


For commercial spas, the manual will help you identify the heating element located among the electronics in the control box. Once you locate the heating element in any type of spa, perform these tests:

  1. Test for the number of amps in the heating element using an amp meter. If the voltage supply is 110, you should read 15 amps. If the voltage connected is 220, you should read 25 amps for the heater. Anything other than that means the heating element is faulty. If the amp test did not show any readings yet the voltage had readings, the heating element should be replaced as it’s faulty. 
  2. Check for the integrity of the pressure switch and the filter. If you run the spa without the filter and the contactor closes when you have the proper readings as in the previous test on the heating element, you need to replace the filter. If the filter had no effect on the working of the spa, you need to replace the pressure switch

Both of these tests require having a meter for the amps and volts with a medium-level skill in wiring. If the spa won’t heat, it won’t bubble and needs to be fixed first.

5. Faulty Heater Contactor

The contactor to your spa works by closing the circuit then breaking it in accordance with the amount of heat and voltage flowing through it. This mechanism depends on the effectiveness of the connected components such as the pressure switch, thermostat and the hi-limit switch. If one of them doesn’t work properly, the contactor will also not work as needed. 


Test for the amps in the contactor the same way you did for the heating element while expecting the same results. If they’re not the expected results, you need to replace the contactor.

6. Faulty Fuses or Breakers

Another cause of the spa not heating water is a faulty fuse or circuit breaker either on the spa itself or on the house. Both of them are meant to prevent power surges beyond certain levels. If there’s a power surge, they’ll both cut off the power to preserve your electronics. 


For a blown fuse, you’ll need a new one of the same type (carry the blown one to the shop). For circuit breakers, you’ll jut need to return them to the original position for the spa to work again. If the circuit breaker appears to break easily, check its voltage since the spa may be overloading it. In such a case, get the circuit breaker with the right electrical rating. 

7. Burnt Wires

Is some cases, the culprit would be burnt wires causing your spa not to heat the water. Like fuses, wires can get overloaded with electrical current leading to the burning. This can be intentionally done by the manufacturer to keep the rest of the spa safe or could be a poor quality spa in general. 


Replace the burnt wires with a new set of wires and some insulating tape and you’re good to go.

8. Faulty Thermostat

The thermostat plays a vital role in maintaining the temperature of the water in your spa. When it gets too hot, it stops the heating process. When the temperature drops below a certain set figure, the thermostat turns the heater on again.


Replace the faulty thermostat with a new one. They’re usually not costly and may be tough to fix.

When you establish the cause of your problem as far as the spa not heating water goes, you can easily find the solution to the same as detailed above. For the very complex spas, you’re better off calling in an expert or returning them to the manufacturer. 

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