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What Is The Ideal Hot Water Bottle Temperature?

Updated: Jan 21, 2023

Ever wondered how warm the water should be in your hot water bottle? How warm it should be on the outside? We did too!


This article was drafted based on the official instructions we received with our Fashy hot water bottle. Fashy has been manufacturing hot water bottles since 1948: needless to say they know what they are talking about.


Let's dive into it!


hot water bottle temperature illustration

The ideal water temperature for your hot water bottle is 80 degrees Celsius (176 degrees Fahrenheit). Besides the water temperature, the surface temperature of your hot water bottle should be below 42 degrees Celsius (108 degrees Fahrenheit), especially for children, the elderly, and other individuals with sensitive skin.


Regardless of your hot water bottle's temperature, it is recommended to use a cover at all times to prevent direct contact with your skin. Prolonged contact between your hot water bottle and bare skin can lead to burns and rash.


hot water bottle instructions

The right temperature for your hot water bottle


There are two temperatures you need to look out for when using a hot water bottle:

  • The water temperature (the water you pour into the hot water bottle)

  • The surface temperature (the temperature on the outside of the hot water bottle)


1. Water temperature

The first temperature you need to look out for is the temperature of the water you pour into your hot water bottle. As we've explained in another article, you shouldn't use boiling water to fill your hot water bottle (boiling water is 100 degrees Celsius, 212 degrees Fahrenheit), as this may lead to damaging your hot water bottle and burn injuries.


The ideal water temperature for your hot water bottle is 80 degrees Celsius (176 degrees Fahrenheit).


Below are 2 ways you can check you have the right water temperature before pouring it into your hot water bottle.


Boil the water and let it cool down for 3 minutes

Green tea drinkers will know this trick. After boiling water in your kettle, let it cool down for about 3 minutes. This will take the water to a temperature of about 80 degrees Celsius (176 degrees Fahrenheit).


Use a digital water kettle

In these modern times, there are many high-tech kettles for which you can set the desired water temperature. While not the cheapest option if you don't have a digital kettle, this makes your life easier as you don't have to let the water rest and time how long you need to wait before pouring it into your hot water bottle.


Set the temperature to 80 degrees Celsius and let your digital kettle do the rest of the work!


digital kettle

2. Surface temperature

The second temperature you need to look out for is the surface temperature of your hot water bottle (how warm it is on the outside). This is important to look out for as it has implications for your skin and overall experience with a hot water bottle.


The surface of your hot water bottle should be below 42 degrees Celsius (108 degrees Fahrenheit). This is especially recommended if it is used by children, elderly people, or those who have sensitive skin.


A surface temperature which is too high can burn you directly or gradually over time, without you even noticing it.


As not all of you have the time or equipment to measure the surface temperature of a hot water bottle, we took care of it for you!


Main takeaway: use a hot water bottle cover

We calculated the surface temperature of a hot water bottle after pouring 80 degrees Celsius (176 degrees Fahrenheit) water into it.


Without a cover, the surface of the hot water bottle was 51 degrees Celsius (123 degrees Fahrenheit). This is far too hot and may lead to burns if in direct contact with your skin, even if you are not a child, an older person, or a person with sensitive skin.


hot water bottle with thermometer

We performed another surface test using a folded kitchen cloth (about as thick as a bathroom towel or a hot water bottle cover). With the cloth, the surface temperature of the hot water bottle was 41 degrees Celsius (106 degrees Fahrenheit).


Conclusion

If you pour 80 degrees-Celsius (176 degrees Fahrenheit) water into your hot water bottle, you'll need to use a cover or a cloth for safe use.


hot water bottle covered with cloth

Final thoughts

The recommended water temperature for your hot water bottle is 80 degrees Celsius (176 degrees Fahrenheit). If you pour water this temperature into your hot water bottle, you will need a cover to protect your skin from the hot water bottle's surface.


Regardless of how warm the water or surface temperature of your hot water bottle is, we recommend you use a cover or cloth for your hot water bottle at all times to avoid burns and make your experience as enjoyable as possible.


In addition, using a cover will keep your hot water bottle warm for longer. Win-win!

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