Can Hot Tubs Be Used With Cold Water?

Hot tubs are obviously well known for soothing away aches and pains and inducing relaxation via hot water. But, can a hot tub also be used with cold water in it? Sometimes the weather is just too hot to use a hot tub comfortably so is it possible to turn the temperature down and create a refreshing “cold tub”? I decided to do some research and this is what I found out:

So, can hot tubs be used with cold water? You can use a hot tub with cold water and if you turn the temperature down to or below body temperature it will have a refreshing cooling effect. Some hot tubs have a cool mode built-in or you can turn the heater off or just fill up with cold water.

Why use cold water in a hot tub?

So, you have gone to considerable expense to purchase a hot tub probably with the aim of using it’s warmth to relax in the evenings, soothe aches and pains and sore muscles and generally be a comforting place to be. Why on earth would you then consider not having hot water in it but running it cold instead?

Primarily, it most likely comes down to the local climate in your area. If the general temperature doesn’t rise about 30 degrees C at the height of summer or really hot spells are relatively few and far between then the thought of running a cold hot tub probably won’t even cross your mind.

However, if your summers are scorching away in the high 30’s or more and you get prolonged periods of heat then sitting in a hot water hot tub may well be the very last thing that you want to do. Our bodies have to work hard to keep our temperature regulated in a hot tub and if you add in the extra stress of the weather being boiling hot as well it can become extremely uncomfortable to be in a hot water tub. In fact, you are at severe risk of dehydration or heat stroke and it might be a good idea to not use the tub during the heat of the day at all.

If this is the case, and you find that you just don’t fancy using the hot tub during the hottest part of the year then using it as a refreshing “cold tub” may well be a really good plan.

Now, before we go on, I have to point out that there is a bit of an issue with this. In an ideal world, it might be nice to have a cold tub available during the heat of the day and a hot tub available in the evening. Many people find a warm evening soak is the perfect end to the day and sets them up for deep restful sleep – a cold tub really cannot achieve that!

Many newer hot tubs have hot and cold settings but it will still take several hours to make major temperature changes to the water so you do, to a certain extent, need to decide if you want the hot tub hot or cold and then live with it maybe for a few days at a time. The only other alternative is to reheat the hot tub from cold every day which, with a modern hot tub may well be possible but will not be particularly energy efficient at all.

What’s the lowest temperature for a hot tub?

Let’s start from the other end of the spectrum to see what the usual hot temperature of a hot tub is so we can put things in context. I have a more detailed explanation here but most hot tub owners have their hot tub water temperature set between 36 degrees C and 39 degrees C.

It’s also worth remember ing that most people’s body temperature is around 37 degrees C. 

Let’s also just check-in at what the average temperature of a swimming pool is. Most pools are kept between 25 and 28 degrees C and anything under 21 degrees C starts to feel unpleasantly cold.

Also that the water coming from your cold tap is probably around 10 – 15 degrees C.

So, we will probably want our cold tub to be somewhere in the region of an average swimming pool temperature between 25 and 28 Degrees C. This will feel pleasantly cool on a hot day but not be so cold that you can only stand being in it for a few moments. It would be perfectly reasonable, in really hot weather to soak in water this temperature for quite some time and get a comfortable cooling effect.

The other option is to go hard core plunge pool temperature and to use the water straight out of the cold water tap which will probably be at around 10 -15 Degrees C. It will obviously warm up over time if the hot/cold tub is standing in warm sun for example but, when it is first filled the water temperature could well be chillingly low.

Bear in mind that if you do fill with completely cold water then you will probably be only up for a very brief and invigorating dip. In fact, you might struggle to get in the water gradually as it will feel so cold. Often the best way is to literally “plunge” straight in but be extremely careful about slipping on the hot tub and injuring yourself if you do take this option. Also bear in mind that it will be a fairly severe shock to your system to go from warmth into freezing water so, if you have any health concerns at all err on the side of caution.

What’s the fastest way to cool down a hot tub?

The fastest way to cool down the water in a hot tub is to completely drain it and refill with cold water from the tap. If you can time this for when your hot tub does actually need a water change then all the better!

The first thing to do is to add a flushing solution to the hot tub and then to run the jets for half an hour or so. This will flush out any dirt and debris from the inner workings of the hot tub and leave them floating around in the water ready to be drained off. Next, turn off the power and drain the water out of the hot tub. Once it is completely empty change the filters and give the hot tub shell a thorough clean with a commercial hot tub cleaning product. Then give the whole shell a wash down with clean water from the hose to remove any residue of the cleaner.

Finally, pop the drain plug back in and refill with cold water using a hose with a filter attached. If you were doing a hot water refill you would need to start adding chemicals and heating at this point but, as you are using the hot tub cold you can miss this stage out. However, it might well be a good idea to still balance your PH levels and to check your calcium hardness as cold water can still corrode the hot tub’s working parts if it is too acidic or alkaline.

For most people, however, it will make more sense to keep the water you currently have in your hot tub and to cool it down the lower temperature. So, how do you do this?

Use the hot tub’s cooling facility – A lot of more modern hot tubs have heating/cooling controls that will go as low as around 25 degrees C which may well be the perfect cooling temperature. Some models will just not heat the water until it goes below this temperature, a little bit like the thermostat on a house central heating system, whilst others will actively lower the water temperature in a similar way to an air conditioning unit.

If you just turn the thermostat down then you will be saving a lot on your energy bills as the hot tub will just wait for the temperature to fall. However, if you have an active cooling system then it will use energy to cool the water down and also to heat it back up. Many modern systems are very energy efficient but it is all relative – changing the temperature of a mass of water relatively quickly, either up or down does take a fair amount of power.

Switch the heater off – If you don’t have a very low setting on your thermostat or there isn’t a cooling option on your hot tub then simply switch the heater off. You will then have to wait until the water cools down and it will settle at a lower temperature that will be dependent upon the air temperature. Bear in mind that it could well take several hours for the temperature to drop, depending upon how well insulated your hot tub is and there will be some point in time when it’s just a rather unpleasant too cold to be hot and too hot to be cold temperature!

Switch the jets on – To speed up the cooling down process you can switch the jets on so that they regularly turn the water and expose it to the cooler air. The faster and more frequently the water moves around the faster the cooling process. It works in just the same way as pouring a hot drink from one mug to another instantly cools it down.

Remove the hot tub cover – Hot tub covers are designed to be excellent insulators so they will keep heat in very well. If you are trying to cool your hot tub then leaving the cover propped open will speed up the process. You could take it off altogether to really make a difference but it would be worth in this case covering the hot tub with fine netting or something similar to prevent flying dirt and debris from getting in and contaminating the water.

Once the hot tub has reached a temperature you are happy with then reinstate the cover as it will help to keep the water at the correct temperature and prevent fluctuations.

Keep the hot tub in the shade – If the hot tub is in strong direct sunlight and the cover is off it could well slow down the cooling down process. If you have an umbrella or any other type of shade then try to get it to cast a shadow over the water surface for as much of the day as possible.

Is bathing in cold water good for you?

Bathing in cold water has a long and glorious history ranging from the Spartans who bathed in cold water to invigorate themselves for battle through to the Scandinavian tradition of having a sauna before plunging into the snow or ice-cold water right up to the famous “James Bond Shower”.

If you need a quick explanation of the James Bond shower it is explained in detail in the original James Bond books (less so in the films I think). Apparently Bond always started his showers off with warm water and then turned the water to cold for the last few minutes. The effect being to invigorate and energize him ready for action!

I’m no James Bond but I have been to hotel spa complexes where there has been a plunge pool and also an ice-cold shower bucket where you pull a bucket of ice-cold water over your head. Both are supposed to be best enjoyed after a spell in the hydrotherapy pool or the sauna. The plunge pool was certainly breathtakingly invigorating and I literally jumped in and was submerged for a matter of seconds. Personally I found the ice bucket a less positive experience!

So, what are the benefits of cold water bathing apart from cooling you down in very hot weather?

Improved blood circulation – As your body becomes colder the blood rushes to the internal organs to keep them warm. Your body works hard to keep it’s core temperature up and this cardiovascular effort, in moderation, is a strengthening and fortifying exercise.

Kinder to your hair and skin – Cold water is better for your skin and hair and can mean it becomes less dried out and flaky. Cold water bathing can give you a healthy-looking glow and is revitalizing for the skin.

Relieves stress and gives you energy – Cold water is great for giving you an energy boost. All that blood rushing through your system gives you a powerful boost and will make you feel great! Your positive energy will also help to reduce stress and make you feel much more upbeat. In fact, in a study by the Virginia Commonwealth University School of Medicine it was found that cold showers can help fight depression due to the extra electrical impulses sent to the brain in the cold.

Can help with weight loss – According to this study bathing in cold water can stimulate the body to burn fat and calories. If that really is the case then standing in the shower or being in a “cold tub” is a great way to lose weight as well!

Do I need to add chemicals to a cold water hot tub?

The main reason that you need to add chemicals to a hot tub is the fact that, because a hot tub operates at such a high temperature, it becomes the perfect breeding ground for bacteria. In theory at least the risks are far fewer if you are using cooler water.

However, the chances are that you will, at some point, want the water warmer in which case you would need to add sanitizer as usual. There will still be a fair amount of dirt and debris in the water even if it is cold and you may not want to be sitting in it as well! It’s a good idea to use chemicals just to be on the safe side and to ensure that you aren’t put at risk of exposure to harmful bacteria.

The only time when you possibly wouldn’t use chemicals would be when you have refilled the hot tub with cold water and you have no intention of heating it up. It would probably be fine for a brief period of use without chemicals as long as it wasn’t heated at all.

You would then need to drain and refill with clean water when you were ready to start using your hot tub as a hot tub again.