Why is my hot tub not heating (and how to fix it)

24th August 2017 | Debbie Ekins

Help Why is my hot tub not heating?

Everything is going great with your hot tub. You’re loving it. You’re using it every night.

And then, you go out, jump in, and it’s freezing…

You need your hot tub to be hot. Especially in Scotland. Where the thought of cooling off is only appealing during the two weeks of summer that we get.

hot tub not heating

Is you hot tub or spa not heating?

Firstly, check for error messages on your control panel. This can indicate what the problem is.

If you phone someone to come and fix it. Let them know about any error messages. This can help diagnose it over the phone. Allowing you to fix something that might be a minor issue. Or, them to diagnose the fault so they can bring the correct parts and fix it first time.

These are the most common hot tub faults and how to fix them

#1 Water flow problem

If your water is heating up very slowly, or your heating keeps turning off then you may have a flow problem. In this case your control panels may show LF or FLO (or a similar flow message). This means there is an issues with water flow, and not enough water is passing through the heater. As a safety feature, the heater should be designed to cut out.


There are a few possible solutions, to fix this issue or rule it out as a cause.


check Water level

Firstly, check the water is at the correct level. And, if not, top it up. If you spa skimmer is sucking in air, instead of water, this will cause the heater to cut out.


release any Pump air locks

If you have recently emptied and filled your hot tub, you could have an air lock in the system, which means little or no water is getting through the system. To fix this:

  1. Fully open the jets (turn clockwise)
  2. Turn down, or disconnect the heater
  3. Turn on the jets and run for 10-15 seconds if water is coming out.
  4. Repeat until you see air bubbles coming out of the jets.

If you try this and water is not coming out the jets, but you hear the pumps trying to start, then you may have a more serious airlock, which will need released at source. In this case do not try to run the pumps as it may damage them. We recommend getting a qualified technician out to do this to avoid damage to the pumps.


Clean your filter

If you have enough water, and there is no air lock then try to clean your filter. Your filter is responsible for catching all the dirt and debris, so the more you use it, the dirtier it going to get. This can restrict flow. You will have to clean it regularly to avoid this.

We recommend cleaning your filter monthly. And replacing every 6 months. Our top tip is to buy an extra filter when you get your hot tub. Then, when you are cleaning and drying one, you can pop the other in and keep using the hot tub. A spare filter averages around £47 (depending on size).


Check pressure/flow switch

After cleaning the filter, if you are still showing a flow fault, then it may be the pressure or the flow switch. This can be checked by an electrician. If this is faulty it will need replaced and usually costs approx. £40 + labour.

#2 Heater element not working

If there is power at the heater, but the water still ins’t heating, then it is likely a fault with the heating element. An electrician will have to check this for you.


If this is the case you will need to replace the heater element. This will cost approx. £50 + labour to replace.

#3 Control board fault

If there is not flow fault. And there is no power at the heater. And, the hot tub still isn’t heating. Then the most likely cause is fault a control board (or Printed circuit board) fault. The board controls everything in the hot tub. It’s the brain of the hot tub.


Usually the fix for this is a replacement board. This can be pretty expensive. Especially, if you have a chinese spa with an unknown control board

Other issues?

There are a few other things, that are not issues with the hot tub as such. But, that could be causing you to lose heat in your hot tub.


Poorly insulated cover

60% of hot tub heat is lost though the top of the water.

If you have a badly insulated hot tub cover, you could be losing heat quickly. Not only will this reduce the temperature of the hot tub. But, your heater will be working overtime to try and keep it at temperature, and burning through a lot of electricity.

Make sure your cover is in good condition, with a taperd width insulation (eg. 5” to 3”).

Read more at How much energy will my hot tub use. And how to reduce it


Recently filled your hot tub?

On average your hot tub will take about 12-18 hours to heat up. Give it time and if it’s still not heating see the above solutions.


Got an airBLOWER on your hot tub?

Using an air blower is great, and adds a whole new dimension to the hot tub.

But, it will also draw in cold air, which can cool the hot tub down. Using it for 10-15 minutes shouldn’t be an issue. But just be aware that using it continuously can make the water feel cooler.

In summary

Hopefully that has helped you understand why your hot tub is not heating. Sometimes, it’s a small fault. Easy to fix. Other times, you may need to get a part replaced.

If you hot tub isn’t heating. Check for any error messages. And, if you aren’t sure on what to do give an engineer a call, and give them as much information as possible on the fault. This was they can have an idea of what to bring and how to fix it when they arrive, which will keep your repair costs down.


These other posts might take your fancy

How much does it cost to buy a hot tub?

The hidden costs of a hot tub

The best hot tub manufacturers in the world

Do I need a regular hot tub service?


Anything we didn’t answer. Or got a burning question about hot tubs? Get in touch…

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Eagle Leisure – Sales & Marketing Manager

Mission = to arm you with the knowledge you need to make the best buying decisions.

Fuelled by coffee (and naps). Explorer of Scotland and the world.