WATER HYGIENE & SAFETY
The results were telling: meter readings showed virtually no water use during the designated flushing period
Harry Evans
Harry Evans BSc (Hons), MRICS, MRSPH, MIHEEM, MCABE, SVHSoc, is an IHEEM- Registered Authorising Engineer (Water), Chair of the IHEEM Water Technical Platform, and Principal of HDE Authorising Engineers. A Chartered professional with over 40 years’ experience in the design, maintenance, and strategic management of commercial, industrial, and healthcare premises, his career spans a broad spectrum of building and engineering services, underpinned by deep technical expertise and a commitment to advancing best practice.
Beginning his NHS
career in 2000 within the Capital Design Department of Salford Royal NHS Foundation Trust, he later served as head of Operational Estates for over 12 years. In 2015, he was appointed as an Authorising Engineer (Water) for Equans. He now leads his own independent consultancy – HDE Authorising Engineers, providing AE(W) services across NHS Trusts and healthcare organisations throughout the UK, offering independent oversight and expert guidance. He is dedicated to improving water safety standards, enhancing compliance, and supporting sustainable system design. As Chair of the IHEEM Water Technical Platform, he is actively involved in professional development across the sector.
n TVCs at both 22 °C and 37 °C. n E. coli and coliforms. n Pseudomonas aeruginosa.
However, this sense of control proves short-lived. Legionella reappears in multiple locations, raising serious doubts about the effectiveness of disinfection and the integrity of the system. A second full system disinfection is recommended by the water treatment specialist. Recognising the complexity and persistence of the
problem, the school’s engineer – now far removed from his hoped-for tranquillity – calls upon an Authorising Engineer (Water). The stakes are rising, and specialist insight is urgently needed.
AE intervention and technical assessment The AE’s involvement marks a shift from reactive treatment to strategic investigation. He begins with a structured review, asking: n Is there a Legionella risk assessment? n Is there a current Legionella written control scheme? n Were pre- and post-flush samples correctly taken? n What Legionella species were present, and at what levels?
n What is the turnover rate of the cold-water storage tank?
n Are temperatures across the system compliant? n Is any residual disinfectant detectable at outlets?
The findings paint a sobering picture: n A Legionella risk assessment and written control scheme were in place.
n The cold-water tank had not been adequately cleaned during previous interventions.
n Post-flush sampling was incorrectly conducted, invalidating much of the earlier assumptions of systemic contamination.
n Sentinel monitoring revealed cold water temperatures above 20 °C.
n Water meter readings indicated monthly, not daily, turnover of the storage tank.
n Residual disinfectant was undetectable at all test locations.
Systemic colonisation Although the Legionella species identified were non-pneumophila, the water treatment company acknowledged the situation as one of serious systemic colonisation. The AE arranged a meeting with the regional Water Undertaker, and confirmed a critical design limitation: the school is served by a long supply main, which dissipates chlorine disinfectant before it reaches the building. This revelation reframes the issue. Flushoaks Primary
wasn’t simply failing on flushing or cleaning – it was operating under flawed assumptions about system input and treatment resilience. In the light of these shortcomings, the AE advised a
56 Health Estate Journal September 2025
series of targeted interventions to restore control and establish defensible compliance: n Legionella training for school staff. n A review of the Legionella risk assessment and written control scheme.
n Competency checks on contracted-out services (water treatment company).
n Correct post-flush sampling, using validated. procedures (BS7592), resulting in a marked reduction in positive samples.
n Installation of a simple chlorine dosing system at point- of-entry to restore and maintain residual disinfectant.
n Thorough cleaning and disinfection of the cold-water storage tank, carried out with verification.
n Daily flushing of outlets, with flow volumes sufficient to promote turnover and distribute disinfectant.
These corrective actions were implemented promptly. The school regained a level of water safety assurance. The local authority, which had raised concerns about the risk to pupils, received documented evidence of remediation. School closure was averted. The story was far from over, however.
n The Human Factor: when people undermine process
Several months later, monitoring revealed rising Legionella counts, and the engineer once again found himself facing a technical and reputational storm. Daily flushing logs were signed diligently. On paper, compliance was perfect, but suspicion crept in. The AE suggested a simple method of verification: check the water meter before the caretaker arrives, and again after he completes his flushing routine. This would reveal actual flow volumes without needing direct confrontation. The results were telling: meter readings showed virtually no water use during the designated flushing period. Confronted with this data, the caretaker admitted: “I’ve
never flushed the outlets. It’s a waste of water and my time.” This admission reframed the entire case. No matter how well-designed the procedures, or how technically sound the interventions, they were ultimately dependent on human behaviour – and in this instance, one unverified routine had nullified all progress. This scenario exposes systemic vulnerabilities that extend
beyond Flushoaks Primary. In many buildings: n Despite its critical role in water safety, flushing is
frequently delegated to non-specialist staff – such as cleaners, housekeepers, or caretakers – who often receive minimal training. This indicates that it is viewed as an ancillary task, rather than a critical control measure within a coherent safety strategy.
n Documentation is treated as proof of action, rather than a prompt for verification.
n The consequences of non-compliance are poorly understood by those tasked with frontline actions. n Oversight is assumed, not actively exercised.
One person’s inaction can negate thousands of pounds’ worth of intervention, and hundreds of hours of strategic effort
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