Why is My Hot Tub Not Heating Up? (Quick and simple fixes)

There’s nothing worse than dipping your toe into a hot tub only to find it’s not hot or not hot enough! In those situations, many people wonder why is my hot tub not heating up?

Here’s what I know from troubleshooting mine:

Your hot tub heater may be faulty or tripped the high limit switch which can be caused by clogged filters or blockage preventing water from flowing through the heater. Additionally, the thermostat may be faulty, and sometimes rodents even chew threw wires under your hot tub, preventing the heater from working properly.

But there’s a lot more to know about hot tub heating issues and how to fix them. So let’s dive in a little deeper!

Owning a hot tub can be exciting. And having easy access to relax in the warmth of it in your backyard can be very pleasing.

So, what happens if you find out it is no longer heating up for you?

Why did it stop and how can you fix it?

There are many reasons your hot tub might stop heating up. We’ll review all the common problems. Those include clogged and blockages. But they can also include faulty heater elements or thermostats.

More information that you may need can be found below, so you can get your hot tub back up and running properly.

How Do I Know if My Hot Tub Heater is Working?

If your hot tub heater no longer heats your hot tub, doesn’t heat it enough, or it is overheating the water, it means it is no longer functioning properly.

This can be due to many factors, including the following:

  • High limit switch problems
    • This is a safety feature that prevents your heater from overheating or having a meltdown.
    • If broken, the water can end up being scalding hot and the heater will not shut off.
  • Having a low flow from the water
    • This is usually caused by a dirty water filter.
    • Other causes can be clogged pumps, closed valves, or blocked drains.
  • Thermostat issues
    • If your thermostat has a knob, you can test to see if it is broken inside or if the sensor bulb is corroded.
    • If your thermostat has a red arrow, you need to check the cord for damage and make sure it is plugged in properly.
    • Most hot tubs have a knob on the control unit under the hot tub which leads to the digital topside panel. So you’ll want to look at the control unit behind your tub’s panel.
  • Hot tub cover replacement
    • If your hot tub cover is damaged, torn, waterlogged, or sagging, it may need to be replaced.
    • Poorly covered hot tubs can cause heat to escape, making the hot tub not heating up properly.
  • Frayed wires
    • Rodents can chew on the wires of your hot tub, causing equipment to malfunction and for it to no longer heat up.
    • Wires that are melted can also cause your heater issues.
    • As with the thermostat, simply inspect the wiring coming to and from your control panel and look for signs of damage.
  • Cold weather
    • Turning your hot tub off in winter but not winterizing it can cause the hot tub can freeze up, damage equipment, and no longer heat well.
    • To better understand both how to winterize your hot tub, but also the best ways to use it in winter, check out my recent article about using a hot tub in the winter. Just click that link to read it on my site.

It is important to make sure your hot tub is working properly when you heat it. Regular maintenance on the parts is a good idea to implement, so your hot tub will last you a long time.

How Do I Make My Hot Tub Hotter?

To make your hot tub turn up the heat, you need to make sure you follow the specifications for your specific model.

Hot tub companies have limits to how hot you make it due to health concerns and based on normal human body temperature. All modern hot tubs are set to allow a maximum of 104° F. You should not attempt to make it hotter than that.

So obviously start by setting your temperature to 104° F. If you want to ensure your heater is working properly, get a floating thermometer and then, if needed, go through the steps in the section above.

But here are the best tips to maximize how hot you can get it:

  • Turn on your jets
    • As you turn up the temperature, make sure your jets are circulating.
    • This will help heat the whole hot tub better, instead of having cold spots.
  • Installing insulation
    • You can use pink insulation boards to line the inside of your hot tub.
    • You can also use spray foam by layering it on the back of your hot tub, surrounding the pipes, and even the jets themselves.
    • Cheaper hot tubs are often poorly insulated, allowing for greater heat loss
  • Construction foam
    • This can also be used in smaller areas of your hot tub or to cover it ¾ of the way.
    • However, make sure to not block the airflow, and do not cover anything electric or that moves and spins.

It is important to keep in mind; please do not completely tamper with the sensors. It can void the warranty with your hot tub.

One of the biggest issues associated with soaking too long in too hot of a hot tub is dehydration.

Check out all the symptoms of hot tub dehydration, and the best steps to prevent that in my recent article. Just click that link to read it on my site.

How Do I Reset My Hot Tub Heater?

Resetting your hot tub heater can help with various heating issues you may be having, including your hot tub taking too long to heat up or not heating at all.

Different companies may have this located in different places, so referring to your manual is important when following the steps listed below:

  • Turn off the power to your hot tub at the breaker
  • Find your hot tub’s red high limit reset button, which may be on the heater itself covered by rubber. This will be similar to the button on the bottom of a disposal.
  • Next, press the red reset button, which will make a clicking sound when it has been reset.
  • Finally, you need to turn your hot tub back on and make sure it is heating up properly and turned on correctly.
  • If there is no power to your hot tub, you might have tripped the breaker panel switch or the GFCI outlet by accident.
  • Reset the breaker – If this happens to be the case and you do not have any power, you need to flip the breaker panel switch back on or press the reset button on the GFCI outlet to fix it.
  • Then turn the hot tub back on. If it trips or does not work when it is starting to heat up, you have an issue with your control box, the heater, or something blocking the water flow. Refer to the steps in the 1st section above about troubleshooting your heater.

After following these steps, your hot tub heater should be reset, and you will be able to use your hot tub again.

If it is not warming up for you still, then your heating element is probably bad. In that case, you will need to follow the rest of this article to fix it.

How Do I Know if My Heating Element is Bad in My Hot Tub?

Hot tub heater elements are just like an electric water heater element. They can burn out if there is no cooling water around it. They can also just wear out over time.

Heater elements can also be tested to see if there is a short in the heating element that is in the coating surrounding it. To do this, you need a test meter that is set to ohms to see the heating element resistance.

Usually, if they are bad, it will go to infinity (and beyond!) or rise very slowly and will need to be replaced.

If they are good, then they will show 9-12 ohms. Sometimes these heating elements can have a scale buildup from sanitizing with a salt system or using hard water. When this happens, the element’s heat output will be reduced, and it can cause failure with the heating element.

The outer casing can also become cracked and will need to be replaced if this happens.

To prevent any heating element issues with hard water, you need to use a sequestering agent. In plain English, that’s a pH increaser. This will remove ions from the hard water.

You will also have to run alkalinity low at 70-80ppm. But this can reduce the formation of scale on your heating element.

It is important to keep up maintenance on your heating element. That can prevent it from going bad and needing to be replaced.

However sometimes it happens, and your heating element may go bad regardless. If this does happen to you, and the preventative measures did not help at all, you will need to replace it.

Which brings us to . . .

How Much Does It Cost to Replace a Heating Element in a Hot Tub?

If you are a do it yourself type of person that is comfortable with water and electricity, you may opt to replace the heating element yourself.

If you are not comfortable fixing it yourself, you will have to call a professional to do it for you. The cost of hiring a professional to do this can range from $350 to $750. The range depends on your make and model and how easy the parts are to find. And of course, things can cost more in different parts of the country.

However, if you are skilled and comfortable doing it yourself, it costs significantly less.

If you just need to replace the heating element part, it can cost about $30 for parts. If you need to replace the heater, tube, and all surrounding it, it can cost about $120 in parts.

But it does vary by brand, and higher quality hot tubs can cost about $320 in parts.

How to easily replace your whole control box/heater assembly

If your hot tub is over 10 years old, it may also make sense to just get a brand new control box with the heater assembly. This is incredibly easy to install, as it just involves:

  • Turn off the master breaker for the hot tub
  • Close the gate valves on either side of the control box (if you don’t have them, you’ll have to drain the tub)
  • Unscrew the PVC connectors on either side of the control box
  • Open the control box and disconnect the main power line that goes to your breaker panel
  • Unscrew the control box from the wood frame of the hot tub
  • Replace with the new control box and repeat the above steps in reverse order to install it

If you opt to replace the whole thing, which again, is pretty easy, here is my favorite one on Amazon by HydroQuip (click to see the current price on Amazon). At my last house & hot tub, I had to replace mine, and this one worked great!

Keep in mind, if you decide to do it yourself, you need to be experienced in tinkering with electricity and water at the same time.

I’m showing you here steps that I have taken on my hot tubs over the years, but I am not a professional electrician, and my article should be considered professional electrician advice.

If you need an electrician or professional advice, you should seek out a qualified professional in your area.

Did I cover all you wanted to know about why your hot tub is not heating up?

It is important to figure out why your hot tub is not heating up first before you try to fix it.

If you take preventative measures to maintain your hot tub, you may not have these issues in the first place. However, if you do wind up with heating problems, you need to make sure you know what the issue is and use the steps above to fix it.

Doing it yourself or hiring someone to do it for you will depend on your experience and the price. Having a hot tub is a wonderful experience. If you properly care for it, you can make it last a lifetime.

Another common hot tub heating question is how long does it take to heat up when you change the water?

It can actually take as little as 2-3 hours, or as long as 8 hours. That range is because of a few factors, but luckily, many of them are in your control!

Check out all the details in my recent article. Just click that link to read it on my site.

Jeff Campbell

Jeff Campbell is a husband, father, martial artist, budget-master, Disney-addict, musician, hot tub lover, and recovering foodie having spent over 2 decades as a leader for Whole Foods Market.

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