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Water treatment for commercial systems: why getting it right is critical


Water treatment in commercial hot water systems is often underestimated, yet it remains one of the most critical factors infl uencing performance, effi ciency, safety and asset longevity. Across the UK, variations in water quality, particularly hardness, mean that a “one size fi ts all” approach is not only ineff ective but potentially damaging. Steve McConnell, director, ICOM explains how a considered, system-wide strategy is essential if building operators are to avoid unnecessary costs and operational risks


W


ater treatment is key to mitigating three primary threats: the formation of scale, corrosion and biofouling. Each of these


can signifi cantly impair the effi ciency of hot water systems and, in the case of microbiological growth, introduce serious health risks. If left unmanaged, these issues can lead to increased energy consumption, reduced lifespan of equipment and costly remedial work.


Understanding the water supply


The starting point for any water treatment strategy is understanding the incoming cold water supply. While UK mains water is treated so it is suitable for consumption, this does not guarantee suitability for commercial heating equipment. Key parameters such as total hardness, conductivity, pH, chlorides and chlorine levels can vary widely depending on the source and blending practices of local water authorities. Hardness is particularly signifi cant. As water is heated, calcium carbonate becomes less soluble, leading to scale deposits building up on heat transfer surfaces. This layer reduces heat transfer effi ciency, increases energy demand and can ultimately cause premature equipment failure. Even a relatively thin layer of scale can have a disproportionate impact on performance. A thorough chemical analysis of the supply


12 June 2026


Above: Steve McConnell, director, ICOM


water is therefore essential prior to system design or commissioning. This enables engineers to determine whether treatment is required and, if so, which approach is most appropriate.


Treatments and their roles


Where water quality presents a risk, pre-treatment of the cold water supply may be necessary. Common solutions include base exchange softeners, reverse osmosis systems, electrolytic scale control devices and polyphosphate dosing. Water softeners, for example, remove the


calcium and magnesium ions that are responsible for hardness, signifi cantly reducing the risk of scale. However, their application must be carefully managed to ensure compliance with water regulations, particularly where drinking water is


concerned. Treated water can be directed only to the heating equipment, leaving potable outlets unaff ected. Alternative technologies, such as electrolytic


devices or polyphosphate dosing systems, off er scale inhibition without fully removing hardness. The suitability of each method depends on system design, water characteristics and manufacturer guidance. Importantly, any treatment strategy should be


developed in consultation with both equipment manufacturers and water treatment specialists. Incorrect application or poor implementation can introduce new risks, including corrosion or water quality issues.


Design and material considerations


Water treatment cannot be considered in isolation from system design. The materials used, fl ow rates, temperatures and layout all infl uence how water behaves within the system. Corrosion, for instance, is often exacerbated by


the presence of dissimilar metals, oxygen ingress or high conductivity levels. Without appropriate mitigation, such as sacrifi cial anodes or chemical inhibitors, metal degradation can occur, leading to leaks and system failure. Good design practice also includes minimising dead legs, ensuring adequate insulation and


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