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Glycol & Water Quality : What to Know

Water Quality & Glycol Systems

Daniel Cohen 
Sr. Market Developer - Dow Glycol Heat Transfer Fluids 

Is Water Quality Important in a Glycol-Based System? 

Unlike what some popular science fiction movies have taught us, the impurities found in water are not always good – at least when it comes to thermal fluids. This fact is inherently true for any glycol-based heat transfer system where water quality matters.  Overall thermal performance, fluid stability and system integrity are all affected by the quality of the dilution water used with the glycol.

Most of the industrially inhibited glycol concentrates available on the market will react negatively with the impurities in exceptionally hard water. The inhibitors will be attracted to and react with the ions and eventually fall out of the solution, effectively removing the corrosion protection needed within the system.

Why Should I Use a Dow Glycol Fluid?

Dow has studied and tested thousands of samples of their propylene glycol and ethylene glycol fluids in a wide range of water types, hardness levels and added impurities.  They have re-engineered key DOWTHERM™ and DOWFROST™ grades with a patented additive to counteract the damaging effects of hard water and ensure long-term fluid stability and corrosion prevention. 

The following grades contain this patented additive under U.S. patent 5,766,506 assigned to The Dow Chemical Company.
However, other impurities and contaminants, such as chlorides and sulfates, may be present in hard water. These can react poorly with the glycol fluids, leading to byproducts and fluid degradation. It is still recommended to use deionized or demineralized water for heat transfer systems to prevent these reactions.

What Quality of Water Should be Used to Dilute DOWFROST™ Propylene Glycol?

Proper Preparation Prevents Poor Performance - The best way to avoid the issues caused by poor water is to start with high-quality water, free of troublesome salts, ions, and impurities. The table to the right details the maximum levels of these compounds for a system to function without issue. For any closed-loop system fill, it is important to consider the remaining flush water and the quality of water trapped within the system. As always, regular testing for concentration and water quality with a refractometer is recommended to achieve the proper water–glycol solution level.

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