Will a Hot Tub Freeze Overnight? {Step-by-step tips}

Some people with hot tubs live in places that get really cold in winter. Those people take precautions with their indoor plumbing, but is that necessary with a hot tub? Will a hot tub freeze overnight?

A hot tub will not freeze overnight as long as the hot tub has power to keep the water heated. Ensuring the cover is tightly secured will also minimize heat loss. But, in areas prone to frequent and lengthy power outages, draining and powering down may be better to ensure nothing in the hot tub breaks. 

But I once cut the power to my hot tub overnight when temps reached freezing to see how much the water temperature dropped.

Mine only dropped 7 degrees!

But there’s a lot more to know, and in this article, we’ll find out how to keep a hot tub from freezing during a power outage and how long a hot tub can function during winter.

We’ll also explore whether an empty hot tub will freeze and the steps to winterize a hot tub. Finally, we look at what happens if a hot tub freezes.

Let’s dive right in…

hot tub freeze overnight lg

How do you keep a hot tub from freezing during a power outage?

If there’s a power outage, prevent a hot tub from freezing by ensuring the lid is firmly in place. If the temperature is significantly below 28° F, and the power outage is expected to last more than 24 hours, consider adding non-toxic antifreeze to the water and manually circulate it.

Just remember if you add antifreeze, even though propylene glycol antifreeze is non-toxic, it will still need to be drained and rinsed out before refilling and soaking.

CLICK HERE to see the best non-toxic antifreeze on Amazon.

As you come into the winter season, if you know your home is likely to have power outages, it may be worth it to set the temp in the hot tub to the max of 104° F. That way, when the power does go out, you’re starting from the highest temp possible.

You can also get a thermal blanket like this one on Amazon, which floats on the surface of the water to help keep the heat in the water.

As a last resort, use a garden hose and drain the hot tub.

You won’t have the power to use a wet/dry vac to get the excess water out of the bottom, so use towels to soak up as much as possible. Thick pools of water will turn into thick blocks of ice and could damage the acrylic shell.

Lastly, remove the side panel and open the screw-on connectors on either side of the heater tube (the silver tube), usually located under the control box.

That will allow most of the excess water in the pipes to drain out.

How long can a hot tub go without power in winter?

A hot tub can go without power in winter for 3 days without the significant danger of freezing. Ideally, the hot tub has been set near the maximum temperature before the power outage. Then keep the cover closed and locked in place.

The largest amount of energy loss occurs at the surface of the water.

So, it’s smart to have a high-quality hot tub cover. You want one that’s not ripped in any place. If it is, you’ve got to mend it.

A good thermal blanket is also great if you had to go without power.

Simply place it on the surface of the water and cover the tub well. This will ensure that the heat energy is trapped in, keeping the water warm for some time before power is restored.

Is it even worth it to keep your hot tub going in winter?

In a recent article, I shared info relating to whether it’s safe to use a hot tub in winter, what to do with your hot tub during winter, and the average temperature that’s ideal for your hot tub during winter.

Just click the link to read it on my site.

Will an empty hot tub freeze?

An empty hot tub will not freeze if it has been thoroughly drained and dried. Use a wet/dry vacuum to remove any remaining water at the bottom after draining and to suck excess water from each jet. Make sure you wipe down the tub very well and keep it properly covered. 

And remove the filter and store it in a cool, dry place.

Freezing, after all, relates to water. So, make sure the tub is completely drained, and you have nothing to worry about.

Any water that’s remaining in the hot tub has the potential to freeze.

You don’t simply want to empty the water in the shell, but also the remnants in the plumbing. Having water left over in the pipes makes the system prone to freezing and cracking! No, a tub that has been thoroughly emptied would not freeze.

Can you just leave a hot tub empty indefinitely or for a season? 

This is what I explored in a recent article of mine. In it, I shared steps that’ll help you winterize your hot tub, how to empty your hot tub, and what do you do with your hot tub when you go on a vacation.

Just click the link to read it on my site.

Can I leave my hot tub empty in winter?

A hot tub can be left empty in winter as water is what freezes, not the shell or plumbing in a hot tub. Just ensure it is thoroughly drained and totally dry with the lid secured and power off.

But the right thing to do depends on the climate and your preferences. Where I live (Texas), I can and actually enjoy using my hot tub during winter.

The weather is that friendly.

If you live in a place like Minneapolis, Chicago, or Montana, where winter is not so forgiving, you might want to take a break from soaking at this time.

But even then, one of my most fun times in a hot tub was when I was surrounded by snow in freezing weather.

So I would only drain and empty mine if I was going to be away for a month or more or if my area was prone to frequent and lengthy power outages.

And in those cases, it’s best to winterize it. 

What’s that? I explored what it is and how to do it in a recent article of mine. In it, I offered a guide on how to winterize your hot tub in 7 simple steps. Amongst other issues, I also explained whether it’s okay to put antifreeze in a hot tub.

Just click the link to read it on my site.

What happens if my hot tub freezes?

If standing water in a hot tub freezes, it will expand by approximately 9%. As the water expands, it can cause things to crack especially if it is in enclosed spaces such as pipes or equipment. Additionally, standing water in the shell of the hot tub could cause the shell to crack. 


Trust me. You don’t want to experience this.

So if you are winterizing yours or just trying to protect it from what you think will be a lengthy power outage, get as much as of the water out of it as possible.

Obviously, that’s a lot easier if you have power, as you can use a submersible pump and wet/dry vac.

But in the event of a power outage, open the connectors on either side of the heater tube, drain it with a garden hose, and use towels to soak up as much excess water as possible.

Fortunately, hot tub freezes are not a common occurrence. Once you put in place the suggestions I’ve shared, you’d be fine.


In the article, we found out how to keep a hot tub from freezing during a power outage. And how long a hot tub can function during winter.

But we also looked at whether an empty hot tub will freeze and whether it’s cool to leave a hot tub empty in winter.

Finally, we looked at what happens if a hot tub freezes.

Photo which requires attribution:

Half Buried (Dog house and hot tub) by Alan Levine is licensed under Public Domain and was cropped, edited, and had a text overlay added.

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Jeff Campbell