The control of Legionella in hospital water supply systems

New guidelines for preventing Legionella underline the fact that standards for water provision are becoming more stringent. Steve Mines, Divisional Sales Manager, Purite, looks at Legionella and the provision of water systems

Water requirements for healthcare facilities vary depending on use – e.g. water for rinsing surgical instruments differs from that for dialysis

Infection control is high on the agenda for facility management companies and contractors in the healthcare industry and Legionella within hospital water systems can pose serious threats to patients. Aside from causing expensive problems and inconvenience, Legionella can proliferate rapidly over a wide area if not properly controlled, causing potentially lethal damage to health as it spreads.

The current UK Health and Safety Commission’s Approved Code of Practice (ACoP) L8 provides guidelines for Legionella control, and Purite has become accredited with the Legionella Control Association’s (LCA) qualification on the Control of Legionella in Hot and Cold Water Systems to complement its already broad in-house process knowledge.

The LCA document Control of Legionella in Hot and Cold Water Systems describes Legionnaires’ disease as ‘a potentially fatal form of pneumonia that can affect anybody, but principally affects those who are susceptible because of age, illness, immunosuppression, smoking etc.’

It is caused by Legionella pneumophila and related bacteria. Legionella bacteria can also cause less serious illnesses that are not fatal or permanently debilitating. The collective term used to cover the group of diseases caused by legionella bacteria is Legionellosis.

On average, there are approximately 200–250 reported cases of Legionnaires’ disease each year in the UK, although the total number of cases of the disease may be generally underestimated

On average, there are approximately 200–250 reported cases of Legionnaires’ disease each year in the UK. It is thought, however, that the total number of cases of the disease may be generally underestimated. About half of cases are associated with travel abroad. Infections that originate in the UK are often sporadic, for which no source of infection is traced. However, clusters of cases also occur and outbreaks have been associated with cooling tower systems and hot and cold water systems in factories, hotels, hospitals and other establishments.

The Code of Practice describes how risk should be identified and assessed, before offering guidance on the control of Legionella covering treatment programmes, monitoring, cleaning and disinfection and, crucially, design and construction.

Specifying purification systems

The right specification can be made only by first carefully considering the performance requirements of a hygiene-critical environment. For example, the requirements of sterile water for rinsing instruments is different from those of water for dialysis. Regardless of each specific application, traceability of source is another essential requisite in today’s demanding healthcare environment.

In all applications, but particularly within the healthcare sector, a check-list will help ensure that no crucial issue is overlooked during the specification process. That checklist needs to include questions such as: What level of purity is required? How much water is required? What are the costs and operational demands of maintenance? Some of these questions may sound obvious but are not always sufficiently considered. However, they are all key questions that must be addressed to move towards the selection of the most efficient system.

In the UK, the NHS issues documents that specify the requirement for purified water used for decontamination. These documents provide guidance on aspects such as water quality, operation and maintenance of washer disinfectors and endoscope re-processors, as well as information on the purchase and installation of equipment.

To achieve the desired water quality specified by the NHS for decontamination applications, several stages of treatment are required, and due to the variations in feed water quality that are measured from site to site, the scope of pre-treatment may vary considerably. However, the core purification process required for decontamination applications is reverse osmosis and the mineral standards specified by the NHS will typically be met by a single-pass reverse osmosis supply.

Expert input

A supplier of water purification systems should ideally have the capability not only to supply but also to design, specify and install a system, rather than delegate to outside contractors. This allows more useful opportunities for consultation, which in turn offers healthcare technologists the opportunity to use their own experience and expertise to help specify the design of either a bespoke system or the commissioning of new equipment. Another benefit of enlisting the services of an expert supplier early in the planning stages is that such a partner will have facilities in place to ensure testing and compliance with industry standards.

Units for renal use are now available with an in-built nocturnal dialysis routine

In defending against Legionella, compounds are used that may be dangerous in their own right and must therefore be removed with additional tools beyond reverse osmosis. This topic was referred to by Dr Nicholas Hoenich, Faculty of Medical Sciences, Newcastle University, in his paper ‘Water requirements for haemodialysis and related therapies’.1

Hoenich said that a survey carried out in 2010 by Gerald Boyle on behalf of the Association of Renal Technologists, highlighted that only 27% of the renal units in the UK have a direct mains feed, with many renal units drawing their water from the main hospital supply. Such systems frequently incorporate a storage tank, and to prevent the growth of Legionella bacteria compounds such as silver-stabilised hydrogen peroxide (SSHP) may be added. Due to its molecular weight, the reverse osmosis (RO) plant does not remove the hydrogen peroxide, and unless there is adequate carbon filtration dialysis patients may be exposed to hydrogen peroxide leading to methaemoglobinemia or haemolysis. Hospital engineering staff should be aware of the potential risk attached to the use of such chemicals to dialysis patients, and their introduction into the hospital water supply should not be undertaken without prior consultation with renal services.

Around 50% of the water treatment facilities for haemodialysis in the UK are at least 10 years old and so are due for refurbishment or replacement

It was also noted that around 50% of the water treatment facilities for haemodialysis in the UK are at least 10 years old and so are due for refurbishment or replacement at a time of funding pressures on the NHS. Potentially, it is possible to extend the lifetime of equipment used for the treatment of water with some diligent maintenance.

With increasingly stringent legislation, such as the current Health and Safety Commission’s Approved Code of Practice (ACoP) L8, specification becomes ever more challenging but hygiene – and ultimately safety – is enhanced.


1. Hoenich NA, Levin R, Ronco C. Blood Purif. 2010. Vol 29 (2), p81–5. Doi: 10.1159/000249212. Epub 2010 Jan 8.