Water Management
Stephanie Allchurch is product development manager at Altecnic
Water system safety in healthcare
Stephanie Allchurch discusses the two main physical methods that can be used to disinfect a water system - chemical disinfection and thermal disinfection
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ontrolling the safety and hygiene of any water system is not as easy, with a number of factors for healthcare facilities managers (HFMs) and water safety groups (WSGs) needing to consider. Water safe plans (WSPs) must be integrated to ensure the most effective means of continually providing safe, wholesome drinking water. Most importantly, a WSP should aim to control waterborne pathogens (including pseudomonas aeruginosa), which can pass from a water system and then from patient to patient. Chemical disinfection, often called ‘biocidal treatment’, of a water system involves contractors introducing chemicals, often chlorine dioxide, into the water system and running the taps through all the pipework within the water system. The taps are then closed to allow the chemicals to kill live pseudomonas within the water system. However, the selection of appropriate chemicals is extremely complex and is dependent on a number of factors, of which are much more prevalent in a healthcare setting. For example, often biocides introduced into hot water systems are ‘gassed off’, and when they are placed in cold water systems (more specifically drinking water systems) they must be monitored to ensure that they do not exceed prescribed concentrations for drinking water. The Health Technical Memorandum 04-01 Part A- Design, Installation and Commissioning (HTM04-01-Part A) suggests: ‘Where biocides are used to control microbial growth in water systems…meticulous control and monitoring programmes should be in place if they are to be effective.’1 As well as impact on the water quality, the components within the water system can be badly impacted by poor choice of acidic chemicals, causing them to deteriorate. HTM0401 Part A states, ‘the detrimental effects of biocidal treatment, such as corrosion of metal components… should be taken into consideration as biocide use may shorten the lifespan
of particular components.’ 1 Proving that, no matter the quality of the components within the system, chemicals can cause the water system to completely breakdown causing additional operational issues.
Fewer limiting factors It is widely known that Legionella, and other pseudomonas, grow in water systems where water is stored at between 20 – 60°C. Thermal disinfection, however, allows water temperature to be increased to above 60°C, killing the pseudomonas. Although this has far fewer limiting factors to the chemical disinfection of a system, thermal disinfection poses a scalding risk to the end user. For example, Health Building Notes 00-10 Part C – Sanitary Assemblies2 advises
‘Chemicals can cause the system to break down’ that outlets above 46°C present a scalding risk and should be labelled as such. It also advises that thermostatic devices, such as thermostatic mixing valves (TMVs), should be used at each outlet remove scalding risk. To safely use water at temperatures that will thermally disinfect the system, WSGs must specify a TMV that adheres to the testing regime of the TMV3/NHS D08 regulatory standard to ensure the safety of the end user. The TMV3 approval scheme provides assurance that a TMV is tested and deemed safe to use in a NHS
setting. These valves offer a high level of protection, reacting much more quickly in shutting off the flow of water if the cold water fails, or a safe temperature is exceeded. As well as allowing for thermal disinfection, the fitting of a TMV that adheres to these standards prevents the end-user from scalding. ‘Risk of scalding’ is still on the NHS ‘Never Events’ list3, which was last updated in February this year. Although most TMVs installed within a healthcare setting, as long as they adhere to the previously discussed standards, disinfect 95 per cent of the water system, there are still places where pseudomonas can potentially form and grow. A common area is a dead-leg where either pipework has been altered and no longer in use. A full thermal flush of a water system, right up to the outlet is advised to remove the pseudomonas present in the terminal fitting. To do this, each valve will need to be bypassed in order to successfully complete the thermal disinfection. However, this task can be reliant on resource and time, meaning it is costly for trusts. Instead, WSGs and HFMs should aim to source TMVs that allow a thermal flush to take place right to the outlet. The Mixcal Careflo Plus TMV has been designed to meet the requirements of BS 7942:2000 and the NHS model engineering specification D08 for use in healthcare settings, hospitals, care homes and schools. This model allows a facilities manager to use a special tool and the manual override function, which ensures thermal disinfection is performed through to the outlets, enabling a complete rather than a partial flush. There are new components being developed, and some already available, which will help to limit the risk to the safety of an end-user while also allowing the best system hygiene to be maintained. As we move forward, new methods of disinfection may be developed to ensure the safety of an end-user is ensured, while also keeping the water system hygienic.
Further reading 1) HTM 04-01- Department of Health and Social Care, April 2017- Safe water in healthcare premises (HTM 04-01) - GOV.UK (www.gov.uk) 2) HBN 00-100- Department of Health, 2013- HBN_0010_Part_C_Final.pdf (publishing.service.gov.uk) 3) NHS Never Events- NHS Improvement, Jan 2018 (UPDATED Feb, 2021)- 2018-Never-Events-Listupdated-February-2021.pdf (england.nhs.uk) OCTOBER 2021 | ENERGY IN BUILDINGS & INDUSTRY | 29
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