How to Insulate a Hot Tub for Winter


OK. The weather is starting to cool down as fall approaches, the apples are falling naturally off the trees in our yard and bringing in the yellow jackets and days are getting shorter, so maybe it’s time to look into how to insulate a hot tub for winter…


Most hot tubs come ready-supplied with an insulated cover, regardless of whether they are inflatable, hard-sided portable hot tubs or the more up-market sunken spas, along with insulated sides, either foam-filled or with air-pockets that act as an air barrier to retain the heat.

 Our Bestway SaluSpa AirJet Helsinki 6-Person Inflatable Hot Tub,
Our Bestway /SaluSpa AirJet Helsinki 6-Person Inflatable Hot Tub


You may be thinking, as most inflatable manufacturers recommend emptying theirs once the temperatures drop to 40F and storing away for the colder months, that is the norm, but there are many hard-sided portable hot tubs and especially the sunken ones where they can be used through the winter season.

In fact, the one we have at present is an inflatable with a frost protection system built-in, a Bestway 54190E SaluSpa AirJet Helsinki 6-Person Inflatable Hot Tub, and is supposed to be good and purposefully built for winter use, but to be truthful, we have not had it long enough to test it out in the colder months so far – we’ll be doing a full report on that in the coming summer, but so far, it’s great and does what it says on the tin.

So, assuming you want to use your hot tub, regardless of type, during the winter season there should be no reason why you cannot, providing the heat is maintained, your power source doesn’t fail and maintenance is continued.

Naturally, it will cost more to keep the temperature up, but there are a few ways you can get around that – see later.

Obviously adding extra insulation is a must to your hot tub, especially underneath as it is one of the quickest ways the heat is robbed from your water in the depths of winter, and the last thing you want to be worrying about is your hot tub frozen pipes repair costs.

Let’s consider this starting at the base, where you can lose up to 30% of your heat very quickly.

Have you got it set up on foam rubber deck tiles or some sort of heat resistant barrier to retain the heat like we have? They come in different thicknesses and colors to suit your hot tub or surroundings.

I’ve also seen them set up on timber deck tiles, but I’m not so sure about that regarding rotting.

We use 3/4 inch deep, soft foam rubber interlocking and waterproof floor tiles which help considerably, even in summertime, plus there’s more cushioning on the bottom of the pool which means more comfort.


We have them set out a little over two feet all around wider than the hot tub so that when we get in or out we are not carrying anything on our feet into the water to puncture the hot tub – just a non-slip safety measure on our part.

How about using a few thermal blankets as a barrier underneath, or another option you may consider if your hot tub cover has seen better days and is not an inflatable type, why not use that one underneath and replace with a better one on top for winter use?


As well as the insulated top cover, why not install one or two inexpensive thermal blankets underneath the cover – simply adding those extra layers will improve heat retention no end.

Most are touted as being ‘solar’, but when used underneath the cover, sitting directly on your water, that meaning does not apply – but the extra depth of air bubbles helps considerably in retaining heat in cold spells.

You need to remember that we bathers are the ones feeding any bacteria present in the water, so the more the tub is used, the more bacteria will develop and because it is so well wrapped up to keep the heat in, there will be very little natural drafts to help clear bacteria away, they will multiply much quicker.

So, regardless of whether you use your hot tub regularly or not during the winter season, you’ll still need to shock the water on a weekly basis if used regularly, but you can extend the time scale if used less often, maybe 10-day intervals, but make it no longer than every two-weeks.


So, let’s look at the inflatables first…

SaluSpa Palm Springs AirJet Inflatable 6-Person Hot Tub
SaluSpa Palm Springs AirJet Inflatable 6-Person Hot Tub


Inflatable Hot Tubs

Usually, these are deflated in late Fall when temperatures drop down to 40F during the night – normally recommended by different inflatable hot tub manufacturers, to be emptied, dried and stored away in some frost-proof area for the winter season.

This is assuming your low winter temperatures are below 40F.

This is all down to air frosts occurring before ground frosts owing to the dew point chilling metal water piping despite the air being slightly above freezing.

If you have a two speed pump built into your inflatable hot tub, then you can set it on the lower speed to help reduce costs, as well as reducing the temperature by around 10 or 15 degrees and reducing the timing of heating, meaning it will be ready for action when returned to normal in a matter of four to six hours depending on its size.

The main problem with inflatable hot tubs and winter use is the fact the heater/pump unit stands away from the main body of water (the heat reservoir).

Should any failure occur, either mechanical or electrical, then this part is very susceptible to freezing up owing to the lack of insulation.

It naturally needs cooling to keep the pump from overheating, and most use air ducts through this part to provide the necessary bubbles, so you will see there is a great chilling effect to be considered during the winter season – plus you don’t want chilled air entering your hot water, otherwise it’d soon be like a fridge…


Hard Sided Portable Hot Tubs


Generally speaking, for hard sided portable hot tubs, keeping the temperature up to 104F is usually recommended if you are going to be using it often, but many owners keep their temperature down by around 20F (84/85F) to help economize as they tend to use their hot tubs less frequently, but with a little forethought it can be upped to 104F in a matter of less than 8 hours.

Some of these hot tubs have two-speed pumps as mentioned above, so that circulation is slowed down and heating can also be time-controlled to give more direct savings, but if you have a single speed, the only option is to reduce the temperature and maybe control the pump timing yourself.

As a rule of thumb, all hard-sided portable hot tubs are safe to use throughout the winter, but there are different grades of hot tub to consider.

Ones with a single pump and pump speed – the plug and play varieties, can be run safely during the colder weather, and ones with two speed pumps are designed for real winter use where the slower speed is adequate to continue the flow while maintaining thorough circulation (meaning the water won’t freeze up), while reducing the power needed to continue pumping.


Confused about the varieties available to you???

Why not click here to check out our page regarding hard sided portable hot tubs to make matters clearer?


What’s the best temperature for hot tubs in winter?

The simple answer here is whatever temperature you feel comfortable at in the hot tub, remembering the water will feel hotter owing to the cooler outside air, but your body temperature will still be about the same, so 104 may feel too hot initially but your body will acclimatize easily.

If on the other hand, you mean what’s the best temperature for hot tubs in winter regarding keeping the water warm enough to stop freezing, then if you aim around the 84/85F mark you will not go far wrong as you’ll have at least a full day minimum with heating failures before any damage is done and it will give time to drop the water and protect your hot tub.


Should I drain my hot tub for the winter?

This is entirely your choice and provided it is insulated properly for winter use, there should be no problems.

Usually, many inflatables are not covered if they freeze up through trying to use them in freezing weather, but this is all down to the individual and any unforeseen events like heating or pump failure causing problems.

Hard-sided portable hot tubs and sunken spas, tend to be made for permanent use so there is really no need to drain this type of hot tub, unless of course, you want to avoid using it over the winter.

After all, these are the type used most in cold climates like Canadian winters.


Will a hot tub freeze overnight???

The answer to this one is a definite NO…

It would need to be in the middle of an ice age for it to freeze up overnight if it had been up to 104F the day before, and even then, providing there is no power failure and the pump is running, even slowly, everything would be savable.


How to winterize a hot tub antifreeze

This may sound like magic, but it is not as it first appears.

Normal engine antifreeze is corrosive to hot tub piping and pumps, so this antifreeze is the type used in RV’s and caravans in their water supply – a non-poisonous antifreeze.

In this case, the hot tubs are drained and around 3 gallons of antifreeze is poured into the filter piping and squirted into the jets so that it sinks into the underfloor piping – mixing with any existing remnants of water, providing an antifreeze mixture capable of resisting the freezing weather.

The problem is there is not enough liquid in there to make sure it is circulated properly, so it is a bit hit and miss.

It is not, as I first thought before we got into hot tubs, simply a case of adding gallons and gallons of antifreeze to the hot tub water to provide protection.

That would cost a fortune, especially if it is drained out with regular use – and what would it do to your skin?

One thing we now have is an emergency hot tub heater just in case the power fails, which happens quite a lot for us. It is a Pentair propane pool heater using propane with a car battery and converter for a power source as it only drives a pump.

We have a page showing the different types available from propane, natural gas and fully electric if you are interested here.


Here’s hoping that’s helped you out and given you an understanding of how to insulate a hot tub for winter use?

So now it’s our turn to ask a favor…


One thing we have failed miserably to find is a thermal blanket that can be wrapped around the sides of our hot tub just to give us further peace of mind.

I imagine this would be easy to make if you want to make one yourself, but trying to find a commercially produced one on the net has come to a dead-stop.


Maybe that’s an opening for some enterprising individual?


It would stand as high as the outside walls of the hot tub and would go around the outside of the hot tub, maybe three or four inches thick and would be filled with foam bubbles or something of that insulative nature.

With a drawstring at the base and top, it could be overlapped if it is too long for any particular hot tub, and the lid (even a slightly larger one) would keep the wall insulation in place, that way increasing the usage during the colder spells and keeping any rain or snow from getting between the hot tub wall and the insulation blanket.

Another option we’ve come up shy on is for when we are using our hot tub less during the winter season where we want a simple sensor to tell if the flow had stopped should the pumps fail, or another problem is if the heater fails, maybe with Bluetooth to a phone, like we have with our pHin Smart Water Care Monitor, sending an alarm when the flow stops or water temperature drops to 50F or so.

There’s bound to be lots of suggestions other people have to make our lives less worrisome, especially regarding cold weather hot-tubbing.

Any suggestions would be gratefully received.

If you can think of any, or maybe you have suggestions on how to insulate a hot tub for winter to help others out, drop us a line, as there may be something already being produced that we are not aware of that would be a big help.

Thanks, Lisa

One thought on “How to Insulate a Hot Tub for Winter

  1. I’ve been trying to find an insulating blanket for the tub walls with no success either. My thoughts are to build an insulating outer wall/blanket and use a commercial blanket on top of the hard insulating cover. I do understand that there may be a heat buildup problem near the motors so there will need to be venting space.

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