Water treatment: The foundation of efficient and reliable commercial heating systems
As commercial and industrial heating systems become more sophisticated and building operators face increasing pressure to improve energy efficiency and reduce operational costs, Steve McConnell, Director at the Industrial and Commercial Energy Association (ICOM), explains why the critical area of water treatment should not be overlooked.
Whether serving offices, hospitals, hotels, schools or industrial facilities, the performance and longevity of a heating or hot water system is intrinsically linked to the quality of the water circulating through it. Yet, despite its importance, water treatment is too often regarded as an afterthought rather than an integral part of system design, commissioning and maintenance.
The reality is that poor water quality can have a significant impact on system efficiency, reliability and safety. Scale, corrosion and biofouling are the three principal threats to commercial hot water and heating installations, and if left unmanaged they can lead to increased energy consumption, reduced asset life, unplanned downtime and expensive remedial works.
Recognising the importance of this issue, we’ve recently updated our best practice guide, Water Quality Considerations of Domestic Hot Water Systems for Commercial Applications. Developed in collaboration with leading manufacturers and water treatment specialists, the document provides practical guidance for designers, contractors and facilities managers on the correct approach to water quality management throughout the life of a system.
Understanding the water supply
An effective water treatment strategy begins with understanding the characteristics of the incoming water supply. Although UK mains water is treated to ensure it is safe to drink, ‘wholesome’ water is not necessarily suitable for commercial heating equipment.
Water quality varies significantly across the UK due to differing geological conditions and the way local water authorities source and blend supplies. Parameters including total hardness, conductivity, pH, chloride content and chlorine levels can all influence system performance. Of these, hardness is often the most significant.
As water temperature increases, calcium carbonate becomes less soluble and begins to precipitate out, forming hard scale deposits on heat transfer surfaces. Even a relatively thin layer of limescale acts as an insulating barrier, reducing heat transfer efficiency and forcing boilers, water heaters and heat exchangers to work harder to deliver the required output. The result is higher fuel consumption, increased carbon emissions and accelerated wear and tear on components.
A detailed chemical analysis of the cold water supply should therefore be undertaken before any treatment regime is selected.
The updated ICOM guide emphasises that water treatment decisions should always be based on measured water quality data and the recommendations of the equipment manufacturer, rather than assumptions based solely on geographical location.
A tailored approach to water treatment
There is no universal solution to water treatment because every installation is different. The appropriate strategy will depend on the incoming water quality, the type of equipment installed, system design and operational demands.
Where hardness presents a risk, pre-treatment of the cold water supply may be necessary. Common technologies include base exchange water softeners, reverse osmosis systems, electrolytic scale control devices and polyphosphate dosing systems.
Water softeners remain one of the most effective methods of reducing scale by removing calcium and magnesium ions. However, their application must be carefully designed to ensure compliance with water regulations and to protect potable water quality. In many cases, softened water is supplied only to the heating equipment while drinking water outlets remain on the untreated supply.
Alternative technologies such as electrolytic scale control or polyphosphate dosing can provide scale inhibition without removing hardness completely. Reverse osmosis systems may be appropriate for applications where particularly high water purity is required. The key message is that treatment technologies should be selected following consultation with both the equipment manufacturer and a competent water treatment specialist.
Equally important is understanding that water treatment and system design cannot be considered in isolation. Factors such as pipework configuration, flow velocities, operating temperatures and the presence of dissimilar metals all influence the likelihood of corrosion or scale formation.
Good design practice, including minimising dead legs, maintaining correct flow rates and considering the use of sacrificial or powered anodes where appropriate, can significantly reduce long-term operational issues.
Commissioning – the critical stage
One of the strongest messages in the updated ICOM guidance is the importance of correct commissioning procedures. Before a commercial heating or hot water system is brought into service, it should be thoroughly cleaned, flushed and, where necessary, disinfected to remove installation debris, contaminants and microbiological hazards.
Firing plant before the water supply has been checked and, where required, treated can result in almost immediate scale deposition on heat exchange surfaces. In severe cases, this can damage equipment and may invalidate manufacturer warranties.
The guide recommends that representative water samples are taken and analysed throughout the commissioning process to verify that the required water quality has been achieved. Water quality certificates, commissioning records and treatment details should then be retained as part of a dedicated Water Treatment Logbook, creating a documented record for future maintenance and compliance.
Water treatment is an ongoing process
Perhaps the biggest misconception is that water treatment ends once a system has been commissioned. In reality, it should be regarded as a continuous process throughout the operational life of the installation.
Incoming water quality can vary over time, while changes in operating conditions, system modifications and normal wear can all affect performance. Regular monitoring, sampling and inspection are therefore essential to ensure that treatment measures remain effective.
For storage systems, periodic inspection of internal surfaces and sacrificial anodes can help identify developing issues before they become costly failures. For instantaneous and circulating water heaters, changes in temperature differential or flow rate may indicate the onset of scale build-up. Treatment equipment itself, whether softeners, dosing systems or filtration devices, must also be maintained in accordance with manufacturers’ instructions.
Just as importantly, water treatment has a direct role to play in protecting occupant health. Biofouling and the potential growth of Legionella bacteria remain major concerns in commercial hot water systems. Compliance with guidance such as HSG274, combined with appropriate temperature control, monitoring and risk assessment, forms an essential part of a robust water management strategy.
Raising standards across the industry
As the industry continues to focus on energy efficiency, lifecycle costs and sustainability, it is increasingly clear that effective water treatment is not an optional extra but a fundamental engineering requirement.
The updated ICOM guide reinforces the need for a holistic approach that links water analysis, treatment selection, system design, commissioning and ongoing maintenance into a single, coordinated strategy. It also highlights the importance of competence, ensuring that contractors, operators and duty holders have access to the right expertise and training to manage water quality effectively.
For heating contractors, specifying and implementing an appropriate water treatment regime protects the performance of the systems they install. For building owners and facilities managers, it delivers tangible benefits through lower energy costs, improved reliability, reduced maintenance and extended equipment life.
Ultimately, investing in water treatment at the outset is considerably less expensive than dealing with the consequences of getting it wrong.
The updated ICOM guide, ‘Water Quality Considerations of Domestic Hot Water Systems for Commercial Applications’, is available to download free of charge from the ICOM website and provides an invaluable reference for everyone involved in the specification, installation and management of commercial heating and hot water systems.
