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Purpose of guide

Hot water bottles can be great for keeping you warm, whether it’s by warming up your bed in the winter, keeping you snug on the sofa while binge watching a series or on a camping holiday in the summer. 

In addition to keeping you warm, hot water bottles can be great for simultaneously helping you relax, relieve stress, ease aches and pains, and get a good night’s sleep. All of these can be great for your short and long term health.

That said many people simply do not know how to get the most out of their hot water bottle effectively and safely. In this guide we shall walk you through everything you need to know to get the most out of yours.

How does a hot water bottle work? 

A hot water bottle is a rubber or thermoplastic bottle with a hollow inner void into which hot water can be poured and stored. A screw cap lid is used to completely envelope the water from the surrounding air. 

The rubber or thermoplastic bottle has insulating properties which prevent all the heat from the hot water escaping right away. Instead the heat is only able to escape gradually through the bottle and travels by convection to the surrounding space outside, enabling the user to benefit from a sustained release of heat over a long period of time. 

Over time the hot water in the bottle cools down as more heat energy is released and dissipated until eventually it reaches the same temperature as the surrounding room. At this point there is no longer a difference in temperature driving the heat from inside the bottle to the outside environment and it is time to refill your hot water bottle - if you haven’t already done so. 

Choosing the right hot water bottle

These days hot water bottles come in all shapes and sizes and are made using a variety of materials. Therefore, it’s important to understand the pros and cons of each option and choose the right hot water bottle for your specific needs.

The main aspects to consider are size, material, shape and presence of an outer cover.

A large hot water bottle, (which we define to be at least 1.5 litres in size) will be able to store more hot water than a smaller one and hence more heat energy. Due to the ratio between its surface area and water capacity, all other things equal, it can be expected to release heat over a longer period. This would result in you keeping warmer for longer.

Larger hot water bottles are effective when trying to apply heat to or soothe a region of your body such as your lower back as they can target a wider area at the same time. This said, once filled they can often be twice as heavy as a small hot water bottle so people who are not as strong such as the elderly need to take extra care. A full 1.8kg hot water with a cover will typically weigh between 2 to 3kg. 

Smaller bottles are lighter, easier to fill and easier to carry which means they are more effective at providing heat to a specific and localised area of your body especially when you need to lift and support it (e.g. if you are suffering from a stiff neck). Due to these properties, they are also great for children.

Smaller hot water bottles are also easier to look after and store. There is less risk of the hot water bottle becoming damaged as there is less material and less risk of burning and scolding. This is in part because they are lighter and fill time is shorter. 

Hot water bottles are usually made from rubber but can also be made of more sustainable products such as thermoplastics. Although typically more expensive, thermoplastic hot water bottles can often be considered as more eco sustainable as they are made from recycled and recyclable materials. Our thermoplastic bottles are made from 90% recycled materials. Thermoplastic products have the added benefit of not giving off an odour like some rubber ones.

Although most hot water bottles take on the familiar classic shape of a rectangular base with a neck at the top of one of its narrower sides leading to the cap, there are some more innovative designs which have been introduced in recent years. This has been either to improve their usability in certain scenarios or make them more appealing. 

A notable example of a hot water bottle with an innovative shape is the long hot water bottle. They work just like typical hot water bottles but are a lot longer and narrower – taking the shape and appearance more akin to a snake. This gives the hot water bottle a lot more versatility and the ability to warm and soothe several parts of your body simultaneously, lie along a sofa, rest around your neck and soothe hard to reach areas such as your back. Although standard hot water bottles can be used for just about anything, long hot water bottles give you that extra versatility. 

Filling a hot water bottle safely video


Checking that your hot water bottle is safe

You must inspect your hot water bottle before you use it for the first time. Make sure that the hot water bottle is compliant with the relevant British Safety Standards (i.e. BS 1970:2006 or BS 1970:2012). To be certain you should be able to find a daisy like symbol on its surface. 

Whenever you use a hot water bottle first look out for cracks, fading, or small holes that could indicate a dangerous product. Many hot water bottles may show both a production date and/or an expiry date. Replace older or worn bottles to avoid accidents and if you are uncertain it is always best to use a different hot water bottle. 

The outer design of hot water bottles is primarily designed for aesthetic purposes. That said a cover is usually a good safety feature as it limits to risk of scalding and burns from coming into prolonged direct contact with the hot water bottle. If you do not have a cover we strongly suggest wrapping your hot water bottle in a towel.


Filling a hot water bottle

Once you are happy that the hot water bottle is safe to use, unscrew the stopper and pour out any water left in inside.

Fill your hot water bottle with boiling water that has been allowed to cool down to a safe temperature. Fill the water to no more than three quarters capacity. 

Do not use boiling water as this can damage the seams of the bottle and adds to the risk of burns. It is important not to use hot tap water where possible as it may contain impurities, otherwise removed during the boiling process, which can degrade the bottle increasing the risk of accidents.

Once you have finished pouring water, slowly squeeze the remaining air out of the hot water bottle so that the water level rises to just below the top. Then screw back on the stopper making sure it's tight.

Finally use a towel or dish cloth to dry the hot water bottle and the stopper. To ensure your safety wrap the hot water bottle in a towel during use, especially if it does not have a cover. 


Using a hot water bottle to keep warm

Traditionally the main use of hot water bottles has been used for keeping warm and that is still largely the case. There are two main ways to keep you warm with a hot water bottle. The first is by resting on or close to your body and the second is by heating up the inside of your bed or sleeping bag before entering.

You can rest the hot water bottle close to or on you when in and around the house – for instance, when sitting down on the sofa. Furthermore, carry your hot water bottle with you when you are going for a leisurely walk during the winter months or when you are commuting to work on a chilly day.

Hot water bottles are also great for keeping your bed warm when you are about to go to sleep. Simply leave the hot water bottle under your blanket for 5-10 minutes before you intend to enter. Don’t forget to remove the hot water bottle before you enter as there is a risk of injury or bursting once you enter (and fall asleep).


Using a hot water bottle to ease aches and pains 

Many aches and pains including neck aches and muscle aches are common from time to time and, although a nuisance, are often nothing to be overly worried about. If problems persist you should seek immediate medical advice.

If you are suffering from an uncomplicated form of pain or ache then heat and cold products may be effective forms of treatment and relief. Many hot water bottles can double up to provide both forms of treatment with the freezer being used to cool down it down to an appropriate temperature. 

Dr. Brian King from UCL says that, “Heat deactivates the pain at a molecular level in much the same way as pharmaceutical painkillers work." His research showed that when heat of over 40oC was applied to the skin it switched on heat receptors at the site of the pain. These temporarily blocked chemical messengers that caused pain to be recognised by the brain.

On the contrary, cold heat numbs the injury by narrowing blood vessels and slowing down blood flow. This in turn, reduces the build-up of fluid in the affected area. Cold is also believed to help with inflammation and swelling. It relieves pain but does not necessary treat the underlying cause.

Heat therapy is frequently used during rehabilitation, or when a person is suffering from deep tissue injuries, back, neck or muscle pain, joint stiffness, headaches or migraines. Heat has relaxing properties, helping to relax stiff and sore muscles and joints. Heat not only relaxes but also stimulates blood flow and improves circulation, thereby increasing your range of motion and reducing soreness and stiffness.    

Heat therapy is not advisable for treatment of acute injuries or pain, as well as for inflammation, bruises and swelling. For these problems, it is advisable to use a cold treatment such as an ice pack or frozen wheat bag. Cold treatment is best for reducing post-exercise inflammation or pain. This is why you often see athletes having an ice bath following a game. Cold treatment is also effective when the injury is recent, red, inflamed or sensitive.

Simply fill your hot water bottle with ice cold water which can be obtained using the ice moulds in your freezer. Apply the water bottle to the affected area or areas for up to 15 minutes covering the bottle with a towel if there is already no cover. This will prevent injuries to your skin from prolonged exposure. 

Here is a summary of which form of treatment may be most effective for your problems:

Heat treatment:




Stomach aches or cramps

Pregnancy and Period Pains

Ongoing injuries

Cold treatment:



New injuries


Using a hot water bottle to improve sleep and reduce stress

Our modern way of life and recent economic challenges have led to higher levels of stress, anxiety and sleeping difficulties in the general population. It is a well-known fact that long term stress and sleeping difficulties can have adverse consequences on an individual’s health. Although heat products such as hot water bottles cannot target the root causes of the stress and sleeping difficulties, they can be very effective as forms of relieving some of the symptoms. If problems persist for a significant period, then you would be best advised to seek medical advice.

The impact of stress and anxieties along with difficulties in sleeping can be reduced by using heat products such as a hot water bottle. The science behind this is quite simple: heat helps you to relax. It does this by stimulating blood flow and improving circulation around your body. Furthermore, heat also has the effect of making you more comfortable in your surroundings. Have you ever tried to fall asleep in a cold room? Hot water bottles can also be used to warm up your bed before you get in.

Generally a single hot water bottle is sufficient for general blood stimulation around your body. It is important to remember that you should not forget to target the less obvious parts of your body such as your feet. A recent study by some Swiss scientists has shown that it is very difficult to have a good night’s sleep with cold feet.

Hot water bottles containing essential oils such as vanilla, lavender and rosemary, are also able to help fight against stress and sleeping difficulties. As these oils are warmed, they diffuse through the air which can help you relax.

For assistance getting to sleep, place a hot water bottle under your blanket at least 5 to 10 minutes before you intend to enter. Once you are ready to get in it is advisable to remove the hot water bottle first as there is a risk of bursting of scalding.

Alternatively, if you feel that you can’t sleep because it is too hot, you can place the hot water bottle or body warmer in the freezer for a few hours before placing it under the covers for 5-10 minutes. Once you are ready to sleep it is again advisable to remove the product first.


Storing a hot water bottle

Remember it’s the little things you do every time you use your hot water bottle that will help it last longer. 

After each use, it’s important to empty the hot water bottle and hang it upside down to dry. Only once the inside is completely dry should it be removed and stored in a dark, dry location. Exposure to excess sunlight can result in cracks, while storing a wet hot water bottle can result in the growth of mould inside the bottle.

Once a hot water bottle has been identified as too worn to continue to use it is important to discard it right away otherwise someone else may use it without realising.


Young children and hot water bottles

Hot water bottles can be great for keeping the little ones in your life cosy and warm. This said, extra care must be taken when using hot water bottles around young children. You must check the minimum recommended age if it is provided and take extra care to read and understand any instructions.

Children and babies should never be left alone with a hot water bottle, and bottles should not be placed directly on a child’s skin. For use warming a child’s bed, remove the hot water bottle before the child enters the bed to avoid unintentional burns or accidents.

Always check the temperature of a hot water bottle to be used with children. Their skin is more sensitive than the skin of an adult and a lower temperature may be more appropriate.

We also recommend that you place your hot water bottles in a safe place when not in use. As young children may unknowingly damage the hot water bottles if they come into contact with them.


Five ideas for your hot water bottles once you have finished using them 

Tablet/I-Pad Cover

Store your tablet and i-pad cover in your disused hot water bottle in a few simple steps. Firstly, place your tablet over your hot water bottle to make sure it is the correct side aligning the bottom of your tablet with the bottom of your hot water bottle. Then cut above the top edge of your tablet. If you want you could also attach studs at the top so that it can be closed but remember to cut further up the hot water bottle to allow space for this. Once complete you can simply slide your tablet inside.

Knee Cushion

Knee cushions are great if you need to do work close to the ground for instance if you are cleaning, gardening or fixing something. Simply fill your hot water bottle with soft materials such as cotton buds, excess fabric and newspaper until you are satisfied with its softness. Don’t forget to seal the stopper before using.

Money Box/Safe

Hot water bottles are great places to hide your valuable items such as money, jewellery and keys. No-one would ever suspect it and look inside.

Watering Plants

Hot water bottles have been designed to hold water so there are few better household items better at carrying 1 to 2 litres of the good stuff for your plants. Just remember not to fill to the brim as water may escape out if you squeeze too much.


Finally, disused hot water bottles can be great for storing pretty much anything. You may prefer to cut along its width with some scissors to have a more open storage compartment. You can store everything from stationery to paint brushes to flowers.


So there we go...

That's all for now folks. Hot water bottles are great and effective ways of keeping you warm, reducing stress, easing aches, alleviating pains, and helping you sleep. This guide has covered how to get the best use out of yours safely and even how you can recycle them when you have stopped using them.