Water’s high specific heat capacity makes it one of the most efficient heat transfer fluids available. It can absorb and transfer more heat than almost any alternative fluid at a lower cost. Combine this with its low viscosity (which makes it easy to pump), and it’s easy to see why water is the default choice in many applications.

If your facility’s tap water is too hard or too impure, you may need to use filtered, reverse osmosis (RO), or deionised (DI) water. These systems remove most dissolved minerals and ionic contaminants, delivering ultra-pure water ideal for sensitive systems. For chillers with inline deionisation systems, you can achieve higher resistivity levels, ideal for laboratory and semiconductor applications.

Even within acceptable hardness levels, minerals can precipitate out of solution, especially as water is heated and cooled repeatedly. These deposits form scale, reducing thermal performance and causing localised overheating. Untreated water can also promote galvanic corrosion in systems with dissimilar metals.

Water freezes at 0°C and boils at 100°C under atmospheric pressure. If your application operates below +6ׄ°C or above +90°C, water alone won’t be sufficient. In cold environments, you’ll need antifreeze protection. For high temperatures, pressurised systems or alternative fluids like glycol may be necessary to prevent boiling.

Thanks to its low viscosity, water can be moved efficiently with centrifugal pumps. However, if fouling occurs (from scale, bacteria, or rust), system resistance increases, making flow rates drop. It’s important to match pump performance with expected operating conditions – and to include filtration if your water quality isn’t ideal.