What is Antifreeze?

Anti-freeze is a fluid added to a caravan radiator to lower the freezing point and prevent overheating. It means that any water inside will not freeze under normal weather conditions and raises the boiling point, effectively preventing overheating. The Alde heating system and radiators
cannot work properly without antifreeze.

Although its main purpose is to provide antifreeze protection, it has a number of functions within the heating system:

Antifreeze – Prevents your heating system from freezing and working as low as -37°
Corrosion Inhibitor – Prevents hot surfaces in the heating system from corroding over time
Biocide – Also, a biocide, therefore, prevents bacteria from growing in your heating system
Coolant – Prevents the system from overheating giving you a nicely balanced heating system

Selecting the right Antifreeze

Does it matter which antifreeze you use in your heating system? YES, IT MATTERS A LOT!

Antifreeze comes in a few different colours but this is NOT a defined way of telling the different types apart! The fluid that is in an Alde system is an Ethylene Glycol based antifreeze. It is a mixture of Ethylene Glycol and deionised water and often made up of corrosion inhibitor, biocide and colour dyes.

It is important that you make sure you are putting the correct liquid into your heating system, so here is a quick insight into the differences:

Blue – This is usually silicate-based and is common in the caravan and motorhome industry.
Orange – Usually Organic Acid Technology (OAT) based and is more common in European caravans and motorhomes industry than in the UK. The chemical make-up of OAT offers better protection for cooling systems and extended life.
Pink – Usually Ethylene Glycol based fluid (G12++ and G13 antifreeze come in this colour)
Green – Now obsolete. It was often used in older heating systems but should not be used.

It is NOT recommended to mix different types of antifreeze! However, Alde has stated that G13 antifreeze can be mixed with the blue anti-freeze found as standard in most UK systems but it is always better to do a complete changeover.

G12++ and G13 antifreeze are recommended for use in the Alde system.

What Should I Use in my van? – Alde Premium G14 Antifreeze

The G12++ and G13 antifreeze are recommended for use with Alde systems. Alde’s Premium G13 Antifreeze is ready to use solution for topping up caravan and motorhome systems. It is pre-mixed with deionised water for the correct concentration and is recommended to use for the best results in your Alde heating system.

But why is it so special? As a premixed ready to go solution, this antifreeze takes away the time and effort of having to dilute of ethylene glycol and deionised water at a 50:50 ratio. Alde has been making heating systems since 1966, so they are real experts when it comes to creating and
maintaining heating systems.

You can rest assured knowing this product is the best for your system as Alde has designed this antifreeze with their heating systems in mind. In comparison with other antifreeze types, The G13 Antifreeze will last up to 5 years before it needs changing, so it will save you a lot of time money and effort in the long run.

Can I top it up?

When the fluid level starts getting low it is a sign that it is time to top up! This can be done in the expansion tank using Alde’s top-up pump, which fills and vents the system, or manually by slowly pouring the mixture into the expansion tank.

The antifreeze in your Alde system should be a solution of 50% ethylene glycol and 50% deionised water. Do not go below 40% or you may damage the system.

Alde has a great video showing how to top up your antifreeze.


When your heating system has gone cold, you should check that the fluid level is around 1cm above the MIN line. You should bleed the system and if the fluid levels fall during the bleeding process, you must top up again. It is recommended to bleed the system at regular intermissions in newly filled heating systems.

If you need to top up often, that may be a sign that your system needs to be checked as you may have a leak.

Changing Antifreeze in your van

Unlike other antifreeze. Alde G13 Antifreeze that can last up to 5 years, older types of antifreeze must be changed once every year two years. It is possible to change the antifreeze yourself, however, this requires specific equipment that you may not have and any mistakes could damage your heating system, which could end up costing more to replace.

It is highly recommended that you visit your local retailer, who will be able to change the antifreeze in your heating system. This will come at a cost but will give you peace of mind and ensure that your system is properly maintained, saving you a lot more time and money!