WATER SYSTEM SAFETY
The flushing unit will discharge any cold water that becomes stagnant or too warm.
incidence by engineering the conditions that can support the growth of Legionella bacteria out of plumbing systems with better design and specification.
Why are hospitals at high risk? Of course, Legionella is not an issue that only affects healthcare environments – far from it. The data available from the ECDC does not give any indication of the source of the recorded cases, but Legionella does not differentiate between locations; the bacteria will happily grow in any location where the plumbing layout and temperature conditions provide the right environment for them to multiply. As a result, public health is just as much at risk from Legionella in private homes and offices as it is in large-scale public buildings like hospitals and leisure centres. However, there are three major factors that create additional risk in healthcare environments. The first is the sheer scale of the plumbing infrastructure; it stands to reason that the amount of water pipes, water services, and water consumption, in any given environment will increase the level of risk proportionately. The second is the amount of modifications that will take place to the plumbing infrastructure during the service life of a hospital building to enable modifications in layout, extensions to facilities, or change of use of a particular space. The risk factor here is that changes to the layout can create ‘dead-ends’ on the infrastructure; redundant sections of the pipework that remain in place despite the fact that they are capped off. Where this is the case, stagnant water can collect, creating an ideal environment for Legionella growth, because water no longer flushes through this section of the network.
Original build programme Of course, in addition, many healthcare estates include older properties, where plumbing networks date back to the original build programme, and have been altered multiple times. Often no clear
64 Health Estate Journal June 2018
Smart end connections allow the installation of a loop or serial type system.
record is available of the exact location or routing of pipes for either the original installation or subsequent remodelling of the building services. With the advent of BIM models to facilitate accurate legacy management of pipework for contemporary hospitals, we can hopefully look forward to a time where it is easier to map any potential danger points on the network. In the meantime, however, older and repeatedly modified plumbing networks remain a significant cause for concern.
The third additional risk factor for healthcare environments lies not within maintenance and specification of the hospital building, but in the demographic of its occupiers. Whereas Legionnaires’ Disease often simply manifests as cold or ‘flu-like symptoms, and goes undiagnosed in healthy people with robust respiratory systems, among the very young and very old, those with pre-existing conditions, compromised health, or respiratory conditions, it is far from a short-lived and relatively innocuous bug; it’s a killer. Consequently, although cleaning, maintenance, and water flushing regimes are more intensive and Legionella-aware in a hospital than they are in private homes, the combination of the scale of installation, scope of modifications, and the volume of occupants with increased vulnerability to infection, puts healthcare estates at heightened risk.
Control and compliance One of the reasons that Legionella is such a threat to public health is that the bacteria can breed extraordinarily quickly, doubling in number every eight hours in any stagnant water, anywhere within a temperature range of 25-45˚C. As a result, it is a hazard that can develop in heating and cooling systems, showers, baths, sinks, and toilets, as well as drinking water and domestic hot water pipe systems.
While stomach acids will destroy any ingested bacteria, water vapour
containing Legionella bacteria can be released from stagnant water in a flushing toilet, a shower, or a running tap, entering the respiratory system to cause Legionnaires’ Disease. It is a risk that is well known in the healthcare sector, and addressed by HTM 04 guidance, which calls for strict flushing regimes in order to minimise the risk of stagnant water in the pipework. To comply with HTM 04, hospitals must also ensure that taps and sentinel points are regularly checked using thermal probes, and that temperatures are recorded so that the hospital is accountable for demonstrating that water is consistently reaching 50˚C in order to control growth of Legionella.
Not infallible
Such regimes provide important safeguards, but they are not an infallible defence against Legionella. Even the most robust and closely monitored flushing regimes cannot overcome the vulnerability of ‘dead ends’ on the network. Moreover, like all elements of routine maintenance and facilities management, flushing regimes are susceptible to human error, and an area missed or inaccurately logged could be a costly mistake for vulnerable patients. Alongside the protection against Legionella afforded by compliance to HTM 04, there are a number of other sources of guidance and legislation that can contribute to Legionella safety and best practice. The Water Supply (Water Fittings) Regulations 1999, EN ISO 806: 2006 (parts 1-6), BS 8558: 2015, and Part G Building Regulations, all reference Legionella safety, while both CIBSE design guides and HSE ACOP L8 guidance also give clear best practice on mitigating Legionella risk. However, it remains vitally important to understand the risks, and to ensure that they are engineered out of hospital building, refurbishment, and remodelling programmes, as effectively as possible, by following best practice design and specification challenges.
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