WATER SYSTEM HYGIENE AND SAFETY
Above: HydroChem says: “Showers are commonly operated for at least 5-10 minutes, flushing sufficient water to allow the residual disinfectant to take effect.”
Left: The Sydney hospital now uses a ProMinent CHLORINSITU electrolysis system for chlorine dosing, linked to a telemetry system that allows remote monitoring.
treats mains supply water, the level of disinfectant at the boundary will vary depending on the distance from the treatment plant, as well as the condition of pipework leading to the building. Storage tanks will also allow the water to sit idle and dissipate the free disinfectant level over time. Any fouling in the tanks may contribute to the presence of bacteria. Interestingly, the Australian Drinking
Water Guidelines do not provide a limit for either Legionella or HCC, meaning that Sydney Water does not provide testing of these parameters. The independent contractor was sampling 10 locations per month. However, due to the lack of a sampling protocol, these were taken from ad hoc locations. It was also common for the handbasins to be tested. This is often the case, as it is easier for a water sampling technician to take a basin sample because they are less likely to get wet, or indeed to bother patients, in the process. HydroChem suggested that a protocol of eight samples per month would meet the local regulatory requirements, and provided a satisfactory overview of the water distribution system health.
32 Health Estate Journal February 2024
HCC testing could cease, as this is not mandatory in New South Wales, nor according to the EnHealth guidelines (which are generally accepted as ‘best practice’). HCC sample results and follow- up actions detracted from the major hazard – Legionella. Furthermore, the sampling protocol ought to be distributed across all floors, and focused on showers, rather than basins. Handbasins do not present a risk of
creating aerosols – a pathway for infection. Most people only utilise handbasins for a few seconds, which means that the water may be stagnant for extended periods. By comparison, showers are commonly operated for at least 5-10 minutes, flushing sufficient water to allow the residual disinfectant to take effect. Handbasins tend to form significant biofilms at the outlet and at the aerators, giving a false representation of the wider recirculating system. Accepting that healthcare providers (as most industries) have competing financial pressures, our goal was to get the ‘best bang for the hospital’s buck’. Funds spent taking more samples than needed, and testing for something unnecessary, were better redirected
toward other measures that helped in achieving acceptable Legionella results.
Gap 2 – Providing disinfection to the warm water system Reviewing the hospital’s chlorine dosing system revealed that the unit was not calibrated. This meant that despite showing sufficient disinfectant levels, there was nil chlorine present in the recirculating warm water. This loop, at 45 °C, was the ideal location for the multiplication of bacteria. It also should be relatively simple to treat, as it is essentially a closed loop. The site plumbers had little training or support in the operation for the dosing system. This meant that attempts to adjust the system were unsuccessful. We also identified that the sampling probe and injection point were installed sub-optimally. The probe was reading water coming from the water heaters, and the chlorine was injecting disinfectant prior to the heaters. This resulted in a ‘false’ loop. Chlorine tends to ‘flash off’ and become inactive when heated, meaning that the probe was reading a reduced level of chlorine, which in turn dosed more chlorine into the heating loop. Simply switching these
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