the actual requirement, creating excess capacity. Adding low-fl ow fi xtures to systems with oversized storage can further reduce turnover and increase the risk of stagnation. Pipework distribution heat loss: Thermal insulation on hot water pipework reduces heat loss but does not eliminate it; similarly, insulation only slows heat gain in cold-water pipes. Increasing insulation thickness can further reduce heat loss or gain, but congested service routes and limited access may make this impractical. As an alternative to a large centralised hot water system with extensive distribution pipework, low-volume point-of-use water heaters may be considered, subject to the operational needs of the facility. Rainwater harvesting and greywater systems Buildings increasingly collect rainwater or recycle greywater (from sinks and showers) to fl ush toilets, irrigate landscapes and run cooling towers (subject to rigorous treatment and fi ltration). We do however need to look at the overall system and its detrimental impact such as additional plant and equipment bringing Cap Ex / Op Ex, extra space to be constructed and ongoing maintenance that increases the carbon footprint. EA/NHBC/Energy Saving Trust believes such systems have a 30% higher carbon footprint. We’re told that water-hungry data centres may increase demand for water. Some may have been installed with dry/wet cooling when they should have had evaporative cooling towers. Cross-contamination is a severe hazard.
If a physical cross-connection occurs between non-potable and potable water lines, pathogens or chemical contaminants can backfl ow into the drinking water supply. Furthermore, recycled water contains higher organic loads, accelerating bacterial multiplication if stored poorly therefore robust control strategies are required. Solar water heating: Solar thermal collectors absorb sunlight to pre-heat domestic hot water, reducing the load on secondary heating systems. Solar energy is intermittent. On cloudy days or during periods of low building occupancy, large solar pre-heat tanks sit lukewarm. This creates a highly vulnerable “lukewarm zone” where bacteria can thrive. The key is to ensure that the fl uid in the solar panels heats the main hot water store indirectly and typically have a separate
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means of heating to top up when required. Suitability for the UK climate should be assessed with the contrast of seasonal weather patterns. Mitigation strategies In the modern built environment, changes that benefi t one aspect e.g. net zero, can create risks elsewhere. Water systems should continue to comply with the Water Supply (Water Fittings) Regulations 1999 and the Approved Code of Practice and Guidance L8, Legionnaires’ disease: The control of legionella bacteria in water systems. Some mitigations are: • Smart monitoring: Implementing remote monitoring for water fl ow and temperatures reduces manual site visits while tracking stagnation in real time.
• Eco-friendly disinfection: Technologies such as copper-silver ionisation and Ultraviolet (UV) light are utilised to control biofi lms and pathogens without relying on high temperatures or harsh chemical by-products.
• Alternative Disinfection: Supplemental chemical water treatment, such as chlorine dioxide or copper-silver ionisation, can control bacterial growth at lower temperatures.
• Rigorous Filtration: Apply robust multi-stage fi ltration, UV disinfection, or disinfection to recycled water before storage. • Strict Colour-Coding: Use distinctly
marked, purple pipework or use copper pipe for domestic water and plastic for non-wholesome water for all non-potable water lines to prevent accidental cross connections during maintenance. • Air Gaps: Implement physical, non mechanical air gaps (compliant with local water regulations) at all top-up connections between mains water and recycled water tanks.
• Automated Flushing: Install smart, sensor activated fl ushing valves on low-use outlets to regularly purge stagnant water.
Conclusion Before making changes to an existing water system, the overall impact should be risk assessed. Responsible and competent persons within the organisation should validate and authorise any planned changes to ensure water safety is not compromised in pursuit of energy savings. Green certifi cation schemes, such as BREEAM or LEED, require robust Water Safety Plans that balance effi ciency targets with public health legislation; however, these targets should never be achieved at the expense of user safety.
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