Can I use water as a heat transfer fluid?
Water is not an approved standard process fluid for ATC chillers.
For standard ATC products, we recommend Hexid or CoolFlow inhibited glycol-based coolants, which have been selected to provide appropriate heat transfer performance while helping to protect the internal cooling circuit.
If your application specifically requires water, please discuss this with ATC before selecting, filling, or commissioning the chiller.
Why doesn't ATC recommend tap water?
Although water can transfer heat effectively, untreated tap water can create several problems within a recirculating cooling system.
The composition of tap water varies according to its source and location. Differences in mineral content, dissolved salts, biological contamination, and water-treatment chemicals can affect the chiller and cooling circuit over time.
Potential problems include:
- Corrosion – dissolved minerals, salts, and other contaminants can contribute to corrosion of components within the cooling circuit.
- Scaling – mineral deposits can build up on internal surfaces, restricting flow and reducing heat-transfer performance.
- Biological growth – untreated water can support biological contamination within the cooling circuit.
- Freezing – water alone provides no freeze protection, creating a risk of damage if the fluid reaches sufficiently low temperatures.
These issues can reduce cooling performance, increase maintenance requirements, and affect the long-term reliability of the equipment.
For these reasons, untreated water must not be used in ATC chillers.
What does ATC recommend instead?
For standard products, ATC recommends Hexid or CoolFlow inhibited glycol-based coolants.
These approved process fluids have been selected to provide:
- Corrosion protection
- Biological growth inhibition
- Reliable long-term thermal performance
- Protection of pumps, seals, and heat exchangers
The appropriate fluid and concentration should be selected according to the chiller and operating conditions.
What about deionised water?
Deionised water is treated as a non-standard requirement.
DI water has different compatibility requirements from other fluids. Systems intended to operate with DI water require suitable materials throughout the coolant circuit and must therefore be reviewed by ATC.
If your process requires DI water, tell ATC before ordering or commissioning the chiller so that the application can be assessed and the appropriate cooling circuit specification considered.
What if my process specifically requires water?
If your application requires water or another process fluid outside ATC’s approved standard fluids, contact us before selecting your chiller.
Our Sales and Engineering teams can review the intended fluid, operating temperature, and application to determine whether a suitable non-standard solution can be provided.
Do not assume that a standard chiller can be filled with an alternative process fluid without modification or approval.
Can I replace the coolant in my existing chiller with water?
Do not replace an approved process fluid with tap water, DI water, or another alternative fluid without first checking with ATC.
If you are considering changing the process fluid in an existing chiller, provide us with the model and serial number, together with details of the fluid currently in the system and the fluid you would like to use.
We can then advise whether it is suitable for the existing cooling circuit or whether further Engineering assessment is required.
Where can I find more information about process fluids?
See How do I choose a heat transfer fluid? for more information about ATC’s approved process fluids, fluid selection, and alternative fluid requirements.
For standard ATC chillers, the key recommendation is to use an approved Hexid or CoolFlow inhibited glycol-based coolant rather than untreated water.
Contact ATC if your application specifically requires water, DI water, or another alternative process fluid.
