Glycol levels: is your chilled water system at risk?


24 February 2022


When the UK experiences sub-zero temperatures, so the troubles can start for those responsible for managing or maintaining HVAC and chilled water (CHW) systems. During winter months, system pipework is exposed to ambient temperatures low enough to freeze cooling water.

Systems that have not been properly maintained are particularly at risk, or those that have been altered or upgraded (as it may be difficult to evaluate the quality and protection qualities of the water). Cooling systems are often topped up with uninhibited water, subsequently leading to a dilution of the antifreeze and inhibitors.

Incorrect glycol levels at this time of year can impact hugely on any cooling system, potential issues include; system failure, flood damage, voided warranties, increased energy costs and reduced output.

Types of glycol

The two major types of glycol used in chilled water and closed loop systems are ethylene glycol (MEG/EG) and propylene glycol (MPG/ PG). Ethylene glycol offers the most efficient heat transfer, is significantly less viscous than propylene glycol, and unit cost is usually lower. The main drawback with EG however, is its toxicity to humans and animals.

In 2010 Hydratech added Coolflow DTX to their range of process cooling fluids. DTX is a high-performance non-toxic heat transfer fluid that is based on ethylene glycol, blended with a detoxification additive. The game changing fluid combines the thermal efficiency and low viscosity associated to ethylene glycol, with the non-toxic rating of propylene glycol.

How much glycol will I need for my system?

Selecting the correct type and concentration of glycol is very important. The glycol type should already be known and recorded in the commissioning documents or maintenance logs for your systems.

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Hydratech Services can assist with glycol determination analysis if it is not known – it is especially important to verify this for food or beverage process applications.

Too much glycol or too high a % will cause system inefficiencies through reduced heat transfer ability and pumping capacity. Not enough glycol, or too low a % can lead to expensive freeze-ups and potential biological fouling issues.
Typically, external systems susceptible to freezing over winter months will need antifreeze protection down to the lowest expected ambient temperature - with a margin of +10%* advised for safety (*Lowest temps ever recorded in UK -26.1°C. January 1982).

As a guide (taking an average between EG & PG, and considering the differing levels of freeze protection per percentage) an installed concentration of 40% v/v (glycol by volume in water) will give you frost protection down to -25°C.

For year-round protection against internal corrosion, scaling and biological fouling, it is recommended that the glycol is fully inhibited and monitored every 6 months. Hydratech recommend a minimum concentration of 25% v/v for their inhibited glycols – this would provide a freeze protection average of -10°C.

Glycol price soar: why it’s time to consider Coolflow DTX

The cost-saving benefits of dosing a new or existing (retrofit) system with DTX are particularly favourable in the current economic climate. For example, given the current rates, a potential saving of around 80% per installation could be made if DTX replaced PG in a proposed 20,000 litre system (protected to -15°C).

For more information on glycol concentrations, Hydratech’s antifreeze range, or fluid testing to verify condition and frost protection - email: info@ or call 01792 586800.