HOT WATER SYSTEMS
Powered anodes are suitable for areas with lower conductivity, but rely on an external power supply to provide protection.
scale is especially problematic in hot water applications. In contrast, high temperatures, as outlined earlier in the article, are needed to prevent the growth of Legionella bacteria. If hard water becomes an issue, a physical water softener or chemical treatment can be an option.
Drawing up a maintenance schedule Regular maintenance is vital to ensure the safety, efficiency, and reliability, of the system. HSG274 Part 2 provides a checklist for hot and cold water systems. An initial risk assessment determines the frequency of the maintenance schedule and monitoring of the system. As with other systems, this is largely determined by what the hot water system is used for and local needs. The maintenance/ inspection schedule ideally comprises weekly, monthly, and annual checks for different parts of the system. Weekly flushing regimes are essential for infrequently used water outlets such as showers and taps, where bacteria can multiply rapidly. Scale removal is advised to be carried out at similar intervals. However, it is outlined that high risk areas such as healthcare premises might require this to be undertaken more often. Monthly checks for hot water systems mostly concern ensuring that water temperatures stay above 50 °C, and that other system equipment prone to water stagnation, such as expansion vessels, is flushed and purged to drain. Annual check-ups are an opportunity for more in-depth checks, and the cleaning of equipment such as calorifiers.
Finishing off the installation (disinfection)
Due to the tendency of Legionella to proliferate at medium temperatures – especially in stagnant water – HGS274 states the time between filling the system and taking up operation as the most microbiologically dangerous. A risk assessment to identify places where stagnant water can occur, followed by
62 Health Estate Journal May 2019
a commissioning procedure which checks the entire system, should therefore be carried out. It is recommended to carry out cleaning, flushing, and disinfection, according to BS EN806 and BS8558, once the hot water system has been installed. A minimum concentration of disinfection chemicals with minimum application time in the system, followed by a system flush until all chemicals are removed, will ensure the microbiological quality of the system. To protect the aquatic environment, a so- called ‘Consent to discharge’ might be required when the system is drained. To test if the disinfection was successful, a bacteriological sample should be taken a week after it has been performed.
Prepared for the future After the disinfection, and when the system is ready to take up operation, we recommend getting it commissioned by a water quality professional. Commissioning sheets and water quality certificates are then kept for future reference. Sacrificial anodes – should they be used – also require regular check-ups, as they need replacing when worn down to 60 per cent to ensure continuing protection. Any installed water treatment equipment requires regular inspection, too. Other than visual checks, regular water samples should be taken to monitor water quality, especially on a bacteriological level. It is a matter of finding a balance to overcome all the risks as outlined, e.g. controlling Legionella with sufficiently high water temperatures, while also ensuring patient safety via the appropriate installation of TMVs.
Designing a safe and efficient hot water system needs to take into account a number of key aspects. In healthcare facilities, such systems need even more careful attention and scrutiny, as vulnerable patients are regularly exposed to hot water that contains bacteria which – although not as hazardous to those with fully functioning immune systems – could prove a significant health risk to the immunocompromised and very ill. While particular care has to be taken during the
initial design stage, and especially as regards choice of material, to minimise dangers and avoid future problems, regular maintenance and servicing of a healthcare facility’s water system is crucial. This not only ensures good risk management from a patient standpoint – which is essential for healthcare premises, but also from a cost point of view – but also prevents the breakdown of equipment, and ensures its ongoing efficiency.
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For further information, refer to the ‘Water Quality Consideration of Domestic Hot Water Systems for Commercial Applications Guide’, developed collaboratively by members of the ICOM Energy Association. Hamworthy Heating is a member of the ICOM Energy Association, and Andrew Dabin contributed to the production of this document.
Andrew Dabin
Sacrificial anodes do not require a power supply, but rely on sufficient conductivity of the water they are ‘operating’ in.
Andrew Dabin is Product manager for Hamworthy Heating, part of Groupe Atlantic UK, ROI & North America, and has worked in the heating industry for 37 years. Beginning his career as an apprentice service engineer for South West Gas, his subsequent roles included Training manager, Sales manager, Technical manager, New Product Spares Development manager, and Product manager, for major heating brands. At Groupe Atlantic he served as Domestic Product manager and Commercial Product manager prior to becoming Product manager for Hamworthy Heating. He has been involved in numerous projects, and has helped deliver to market products including combi boilers, domestic magnetic filters, controls for domestic boilers, floorstanding commercial boilers, frame and header kits, and interface units. He regularly attends industry body technical meetings for the Heating & Hotwater Industry Council (HHIC), and the Industrial and Commercial Energy Association (ICOM), and reports on changing standards and legislation.
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