The antifreeze in your Alde heating system does far more than protect against freezing — it also prevents internal corrosion and inhibits bacterial growth. Over time, however, the corrosion‑protection additives naturally begin to break down. The good news is that we can accurately assess the condition of your heating fluid with a simple test carried out during your service.
Many Alde owners remain confused due to outdated advice, North American guidance (where a different chemical base is used), and misinformation circulating on forums and YouTube. This confusion is made worse by some antifreeze suppliers marketing their products as suitable for hydronic heating systems, even though they are not Alde‑approved.
There are only four Alde‑approved antifreeze products permitted for use in the UK (Alde Approval 40X0 2024). These are the only fluids that meet Alde’s required chemical specification. 👇🏼👇🏼
When in doubt — especially with a pre‑owned caravan or motorhome — it’s best to replace the heating fluid at your earliest convenience to ensure optimal performance and long‑term protection.
At MDMCS, we use only genuine Alde‑approved antifreeze. It is magenta in colour, protects down to approximately –37 °C, provides full inhibiting protection, and typically offers a service life of up to five years.
Topping up your Alde heating fluid couldn’t be simpler — just use the same antifreeze product that’s already in the system.
If your heating fluid is magenta, it’s very likely an Alde‑approved antifreeze. In this case, you can safely top up with any Alde‑approved product, as all four approved fluids are fully intermixable.
If the fluid is not magenta, or you're unsure of the compatibility, the safest option is to top up with a small amount of deionised water. This will slightly reduce frost, corrosion, and bacterial protection, but it avoids the far greater risk of mixing incompatible antifreeze types. After topping up, the heating fluid should be replaced as soon as practicable with a genuine Alde‑approved product.
