WATER SAFETY
Photos of problems (blocked copper pipe) associated with disinfectant use.
systems. The cold water should be maintained below 20 °C and the hot water calorifier above 60 °C with a minimum of 55 °C at the outlets. The temperature of the return loops should be above 55 °C.5
The detail
Dr Cathy Whapham
Dr Cathy Whapham has worked in contamination control for more than 25 years, predominantly alongside clinical microbiologists, infection prevention and hospital engineering teams on water hygiene programs. She has extensive practical experience of critical contamination and waterborne outbreaks within public and private sectors both nationally and internationally, and provides bespoke training and holistic advice on waterborne contamination, prevention and control strategies for in-premise drinking water distribution systems, the periphery of the water system and wastewater interfaces. Alongside her water consultancy, Cathy manages the Tickmore Orchards and raises native breed Ryeland Sheep in Herefordshire.
of consistent temperature control is critical. The goal of cold water temperatures is not simply to maintain the water below 20 °C, but to ensure that there is no more than 2 °C of heat gain between the influent mains water temperature and the furthest outlets. Therefore, if the influent cold water temperature to the building is 14 °C, there should not be more than 16 °C measured at the outlets. Any areas demonstrating greater than 2 °C heat gain in the cold water should be investigated and corrected. Heat gain may be due to inadequate insulation, a cross connection, faulty non-return valve within the hot water system, or extended periods of stagnancy (which is usually due to underuse). Within the hot water system in healthcare buildings, it is common to find hydraulic imbalance, particularly where refurbishment works have added outlets, where areas have been isolated, or where balancing valves have seized. Whilst calorifier temperatures and returns can indicate appropriate and consistent performance, the measurements at the secondary and tertiary loops, and even at the individual outlet level can be vastly different. Pockets of inadequate hot water temperatures (below 55 °C) may be found when forensically analysing the system in detail.5
This
activity is difficult to support manually, whereas with continuous remote monitoring the performance of a system can be recorded and diagnosed under periods of rest and peak use with confidence and accuracy.6,7 Other methods to manage microbial contamination are via throughput and turnover. The body of water within a building, representing the total volume in the storage tanks, calorifiers and within the pipe network, should turnover at least daily and ideally more frequently. The detail of turnover is also critical, as this ‘one building volume’ of water should pass through each and every outlet and equipment equally and daily. Recognising outlet and equipment use on a daily basis is no easy task and subject to bias. It is not sufficient to assume that if a room is occupied, then the outlets are regularly used. Known low use outlets are often placed on a flushing list with weekly, twice weekly or daily flushing. However, the efficacy of flushing is rarely verified and consequently the use of intelligent automatic flushing of taps and showers is also helpful to maintain consistency of throughput to outlets
36 Health Estate Journal January 2026
which are predicted to be intermittent or low use. Despite temperature and throughput/turnover being the main control measures, maintaining effective performance of either can be problematic, often resulting in microbial growth. Therefore, a number of secondary control strategies can be risk assessed and deployed. One such secondary control is the use of chemical biocides, such as chlorine derived products, hydrogen peroxide or silver and copper ionisation.8
However, the implementation of
a biocide is not a panacea and, in many cases, does not bring about control of waterborne pathogens due to a myriad of survival strategies. In addition, chemicals can have negative or corrosive impacts on materials and surfaces within the water system and may present health risks to consumers from disinfection byproducts.
Biocide efficacy versus environmental persistence of waterborne pathogens Waterborne pathogens have remarkable environmental adaptability and persistence. Many waterborne microorganisms succumb to impacts of hot water temperature and the application of shock or continuous systemic biocide application. However, tolerant microorganisms will survive and thrive under such conditions. Tolerant microorganisms could be described as “professional” water system dwellers that are capable of biofilm formation, utilising nutrients released from dead cells, hiding and proliferating within other microorganism (protozoa) hosts, and sharing their successful traits with other microorganisms.9,10
Therefore, unless a water
system is designed, specified, installed, commissioned and operated continuously under best practice (which is different from compliant with guidance), environmental conditions will prevail which can support pathogen colonisation and amplification. When introducing a biocide, it is critical to undertake a full risk assessment prior to selection and implementation. A literature search should be undertaken to assess the application of particular biocides under operational conditions reflected at the site under consideration.11-13 The presence of organic matter will negatively impact biocidal performance, particularly in terms of dosage. High organic concentrations will reduce the presence of the active chemistry resulting in concentrations that are too low to control the presence of free-living waterborne bacteria leading to a microbial risk. It is also important to understand how that organic
Sam Green /
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