Water Quality & Freeze Protection in Geothermal/Hydronic Systems

Closeup of Test Tubes and Pipette

Regardless of your sector of industry, if you’re using a thermal transfer system, its design can impact significantly on Heat Transfer Fluid and water quality. In a learning resource extracted from CORECHEM’s recent participation in the IGSHPA Dig Deep Webinar series, we explore how thoughtful system design can impact the performance of fluids.

Across virtually all systems that use Heat Transfer Fluids, the design and maintenance of those systems play a crucial role in determining both the longevity of the system and the performance of the fluid it contains. In order to fully understand this, it is important to build a basic awareness of Heat Transfer Fluids and water quality.

Heat Transfer Fluids and Water Quality: The Basics

When it comes to thermal transfer systems, the quality of water used can have a pivotal effect on the performance of the system as a whole. Where poor quality water is used, a number of detrimental effects should be expected. We’ve highlighted these below:

  • Scale
  • Sediment deposits
  • Creation of a sludge in the heat exchanger 

Ultimately, the presence of scale, sediment deposits or sludge will reduce heat transfer efficiency. Indeed, aside from leading to the premature degradation of your Heat Transfer Fluids, other consequences include significant damage to equipment, piping and valves.

Ideal Water Quality Specifications

When it comes to maintaining optimal water quality, understanding the key parameters is crucial. Keep reading for a broad overview of the parameters you should be considering:

  • pH: Typical range 6.5 to 9.0.  Lower values typically associated with higher rates of general corrosion in ferrous and copper alloys; higher values associated with scaling.
  • Total dissolved solids: This is a gross indicator of the quality of dissolved constituents.  Higher levels associated with increased corrosion and/or scaling; used in calculation of scale index.
  • Iron: Use care to prevent iron’s exposure to air; problems possible at >0.5 ppm.
  • Alkalinity: The ability of water to buffer acid, strongly linked to scale and used to calculate scaling index. Usually expressed as ppm CaCo3.
  • Calcium: Linked to scaling of water and used to calculate scaling index. Expressed in ppm Ca x 0.5 = ppm as CaCO3.
  • Carbonates/bicarbonates: These will vary in concentration with pH.
  • Hardness: Linked to scaling and used to calculate scale index; at >100 ppm, scaling can occur.
  • Chloride: this accelerates corrosion of carbon and stainless steels and may be elevated in coastal areas.
  • Manganese: This causes black scale; possible deposits can be detected at >0.2 ppm.
  • Oxygen: This dissolved gas accelerates corrosion and promotes other chemical reactions.
  • Hydrogen sulphide: This dissolved gas with a rotten egg odor attacks copper alloys.
  • Carbon dioxide: This dissolved gas is often present at pH <7.5, GW pressurization keeps CO2 in solution.

If you’re unsure of how to proceed in a way that’s protective of your system, be sure to check with your local county or city water departments to determine the chemical properties of the water that will be used.  If dilution water will be drawn from a well (typically hard water) or the local water authority cannot provide an accurate profile, we recommend having the water tested.

Dispelling the Potable Water Myth

Woman scientist holding flask with checking water quality

Here at CORECHEM, we often hear one myth that we’d like to take this opportunity to dispel. We frequently hear the phrase that “if you can drink it, then it’s good enough for my hydronic system.”

The reality is that while hard water may have all the minerals a human body can process, these same minerals can be devastating to a hydronic system. Minerals in hard water (think calcium, magnesium, iron, chlorides and sulphates) can lead to significant corrosion and build-up, reducing the efficiency of your system and inevitably leading to eventual system failure. 

In those cases where tap water does not meet the standards for quality, deionized water or water that has been processed through reverse osmosis to remove unwanted minerals is recommended. Note that a suitable corrosion inhibitor must be used with DI or RO water even when the treated water is pH neutral.

The Importance of System Freeze Protection 

When considering the impact of system design on Heat Transfer Fluid and water quality, it is important to consider the importance of system freeze protection.

Where untreated water is being used, freezing will lead to expansion, resulting  in costly repairs. By using a fully formulated Heat Transfer Fluid, you can increase protection for your system at lower temperatures than water alone: a valuable “insurance policy” for your geothermal or other hydronic system

 

What Heat Transfer Fluid Do I Need?

Choosing the right heat transfer fluid for your system depends upon a variety of factors in addition to the system itself, including state/local building codes, toxicity, biodegradability, viscosity and more. Our chemical experts are on standby to help you make an informed decision. To get started, browse our full selection or reach out to us now.