Frequently Asked Questions on the Control of Legionella

Control of Legionella

Which system will completely remove the risk of legionella in buildings covered by the Department of Health?

MYTH:

The Department of Health (DH) aim is to eliminate the presence of Legionella in domestic water systems within its buildings.

 

FACT:

The DH stress that it is Legionella suppression and associated risk control which is at issue and the complete removal of Legionella is not seen as a realistic target.

Did a recent independent review by the Department of Health conclude which system is the best?

MYTH:

The Department of Health (DH) has concluded that temperature control is the only system which should be used to control the risk of legionella.


FACT:

A copy of the report from the 'Independent review of evidence regarding selection techniques for the suppression of legionella in water supplies of hospitals and other healthcare premises' can be found: Independent Review of evidence regarding selection of techniques for the suppression of Legionella in water supplies of hospitals and other healthcare premises , and the DH response to the independent review can be found:  Response to Independent Review of evidence regarding selection of techniques for the suppression of Legionella in water supplies of hospitals and other healthcare premises. . It will be seen from the DH response point 9 that 'DH takes the view that whilst the particular technology chosen for legionella suppression is of importance, the use of quality systems to maintain and operate these precautions is also a critical factor in protection and prevention of an outbreak. For this reason, much of the content of Hospital Technical Memorandum 04-01 relates to quality control and maintenance of whichever protective regime is chosen by the local NHS provider.'

The fact that temperature control is the most prevalent technology in NHS properties is based on the free choice of system designers and their continued confidence in this technology.
 

What independent studies are available into the effectiveness of each system?

MYTH:

There are numerous, easily accessible, independent and authoritative research papers/case studies available for the full range of installation types for both systems.

 

FACT:

It is apparent that most of the current case studies are somewhat dated (typically 10 years old) consequently BEAMA will implement some desk based research to pull together a portfolio of the most up to date studies and will make them available as soon as possible on this site.

Does the effectiveness of either system deteriorate over time?

MYTH:

All systems can be expected to operate equally well over the full term of their designed life.

 

FACT:

All systems will need regular maintenance. Thermostatic Mixing Valves (TMVs) will normally require annual testing and/or servicing within a standard hospital building services maintenance regime. Ionisation will require more specialised and regular maintenance checks (e.g. pH testing).

The electrodes used in the ionisation process are sacrificial and as such the amount of silver and copper released will vary depending on their condition. PH and particulate levels in the system also vary and have a significant influence on the ability of the system to control bacteria levels.

What are the impacts on energy consumption of each system?

MYTH:

The seriousness of potential incidences of legionella makes the energy consumption and associated carbon emission impact of system selection irrelevant.

 

FACT:

Across the world, governments and scientists alike are in general agreement that the long term negative impacts of climate change currently pose the most significant threat to civilsation as we know it.

As such the comparative energy impacts of each system must be an integral and important part of the system selection process. The actual delivered energy, i.e. the energy consumed in kWh at the point of use, will be similar for both systems (i.e. crudely speaking, less hot water at 600C compared to more hot water at 430C will require similar energy input). Therefore wasted energy will mainly arise through losses from the hot water storage tank (calorifier) and distribution losses from pipe-work etc. In both cases the actual losses will be dependent on the individual despoke installation design and construction and therefore it is impossible to give a generic 'one is better than the other' response. The energy impacts should be investigated on a case by case basis.

Is there a risk of Legionella proliferation on the seals located within TMVs

MYTH:

TMVs have a specific problem associated with Legionella bacteria accumulating on the elastomeric seals located within the valves themselves

 

FACT:

The use of elastomeric seals is not unique to thermostatic mixing valves (TMVs) and is in fact commonly found in all forms of mixing device. Consequently their removal could only be achieved by eliminating all forms of mixing – this would obviously be impractical. A “rubberless” domestic water system (DWS) is not a realistic proposition (e.g. ’what do you do with showers’) nor is it realistic to deliver a system which is absolutely nutrition free for legionella and other organisms. TMVs allow domestic water systems to be designed and managed in such a way that it is inhospitable to legionella and other organisms but absolute eradication is not, and has never been, a realistic objective.  All of the TMVs on the market today that are TMV3 approved must also be Water Regulations Advisory Scheme (WRAS) approved. In order to gain WRAS approval all of the components of the mixing valve must comply with either WRAS requirements or be tested by an accredited lab to BS 6920.To gain compliancethere arespecific tests to ensure that the elastomeric components do not support the growth of microorganisms.

Also, to put this into context, according to the health protection agency the number of cases of legionnaires disease that are reported to have come from all of the hospitals inEngland and Wales in 2007 was 12, in 2006 it was 4. Compare this with the facts that:

· 541 people per year are admitted to hospital with scaldinjuries, of these 80% are children.

· 22 people die from scald related injuries every year,most of which are the elderly.

Despite these statistics reinforcing the absolute need for temperature control, the BEAMA Water Safety & Hygiene group takes the issue of Legionella control very seriously and are looking into the real issues behind the suggested concerns over elastomeric valves. This question and answer section will continue to be updated on this issue as we develop further information.

Is the Department of Health 'anti' copper and silver ionisation?

MYTH:

The Department of Health (DH) actively discourages the installation and use of copper and silver ionisation systems as a means of controlling the risk of legionella.

 

FACT:

The DH has spent some time and effort over the past two years refuting exactly this type of accusation. Their latest published response:  Response to Independent Review of evidence regarding selection of techniques for the suppression of Legionella in water supplies of hospitals and other healthcare premises. relates to a recent independent review of legionella suppression techniques and highlights DH desire for all options for the control of legionella to be considered. The DH referes to the guidance provided to this effect located in Hospital Technical Memorandum 04-01 (HTM04-01) Part A, Section 15 and also in Appendix 5 of the same document. Example extract as follows: 'The use of ionisation as a control measure will depend on the design of the systems and, in an existing system, their operational history.'

What impact does the hardness or softness of local water have on each system?

MYTH:

The hardness or softness of water is irrelevant to the effective control of the risk of legionella.

 

FACT:

Typical water supplies contain trace minerals such as manganese or chalk. The level of concentration varies around the UK and the level of concentration has a direct effect on the hardness or softness of the water. When water is heated, these minerals deposit themselves in the form of scale on pipework, fittings, etc and can cause loss of system efficiency. For Thermostatic Mixing Valves (TMVs) this problem is no different to any other part of the system and can be dealt with as part of a standard system maintenance regime. However, for ionisation systems the effect of scale build-up on the electrodes will vary the amount of silver and copper ions released into the system. Anti-scaling electrode cells and weekly pH monitoring are needed to maintain effectiveness as the level of ion release must be kept constant.

What are the impacts of retrofitting each system to an existing installation?

MYTH

Both systems can be easily retrofitted to an existing installation.

 

FACT:

As healthcare buildings typically require a range of different delivery temperatures for different applications within their buildings, the hot water distribution system is normally sized to accommodate a water temperature of around 60oC. The hot water is then mixed with cold water to achieve the appropriate temperature required for the local application. Consequently Thermostatic Mixing Valves (TMVs) would be an effective retrofit on a typical system and where appropriate will mix hot and cold water to deliver an appropriate mixed water temperature for each different application.

Ionisation systems may deliver hot water at around 43oC. Consequently, existing pipework and calorifiers will potentially need to be resized (i.e.replaced) to deliver the appropriate amount of hot water for each application.

Applications requiring hot water at higher than 43oC will require localised point of use water heating or an additional separate system installed.

Applications requiring water at less that 43°C will require some form of manual mixing device. The NHS Model Engineering Specification D08 Thermostatic mixing valves (Healthcare premises) specifies four different discharge temperatures for a variety of designations.

What are the ongoing maintenance requirements for each system?

MYTH:

There is little difference in maintenance requirements between the two systems

 

FACT:

Ionisation systems require frequent and ongoing maintenance to be effective. Electrodes must be cleaned (unless they are self cleaning), and replaced regularly. The electrodes used in the process are sacrificial and as such the amount of silver and copper released will vary depending on their condition, pH levels and particulate in the system also vary and have a dramatic effect on the ability of the system to control bacteria levels. The rate of dosage must be adjusted depending on water conditions which can change daily. Testing the water to check its quality and that the system is working must also be done much more regularly and at a significant cost.

The chemical composition of the water to be treated has to be considered before selecting the method of treatment. Silver concentration at sentinel outlets must be monitored monthly and representative outlets monitored annually to ensure it is above 20 μg/L. To ensure effectiveness, silver should be kept at 0.01 to 0.08 ppm and copper at 0.2 to 0.8 ppm.

Temperature control systems will require a much less onerous maintenance regime which is in part prescribed in and directed by HTM 04-01 Part B Operational Management, the NHS Model Engineering Specification D08 also prescribes requirements for TMV manufacturers to include in their installation, commissioning, operating and maintenance instructions and these instructions are also independently vetted as part of the TMV3 Scheme approval process.

What are the wider environmental impacts of each system?

MYTH:

Systems which control the risk of legionella have little or no megative environmental impact.

 

FACT:

The impact of energy consumption and associated carbon emissions are dealth with in question 7: 'What are the impacts on energy consumption of each system?'

There are also some potential non-energy related environmental and health impacts to consider.

Ionisation involves continuous dosing of potable water with siler and copper ions. The dosed water is mainly discharged into the drainage system of the public water supply network although a small amount can potentially be ingested by patients and staff. Where a system contains a high concentration of copper and silver, the long term effects of exposure to this type of dosing, both to the environment and consumers, are currently unknown.

Why is temperature control the 'preferred' system for the Department of Health?

MYTH:

The Department of Health (DH) require the control of the risk of legionella to be delivered through the use of a temperature control regime to the exclusion of other systems.

 

FACT:

DH allows a range of system options for the control of the risk of legionella. DH refer to temperature control as the 'preferred' system in HTM04-01 but this is in the context that the temperature control method is seen to be the most prevalent method in existing and planned NHS buildings. The term 'preferred' has been challenged by at least one manufacturer of ionisation equipment and as a result an 'independent review of evidence regarding selection techniques for the suppression of legionella in water supplies of hospitals and other healthcare premises' was commissioned by DH and published in March 2009.

Will the systems 'fail safe' in the event of breakdown?

MYTH:

All systems can be designed and installed to ‘fail safe’ in the event of any form of mishap, emergency or breakdown.

FACT:

There is no system that can be truly designed as 100% fail safe. Temperature control systems that fail will be identified very quickly as there will be no hot water. This facilitates a prompt repair and provides a clear indication as to when the system is back up and running.

Ionisation systems that fail will not become apparent until the next water quality check or scheduled system maintenance. This could leave the ionisation system maintaining water temperature at 40-45oC for some time without being dosed which in turn could provide conditions which allow for the proliferation of legionella bacteria.

In the Department of Health response to a recent independent review:  Response to Independent Review of evidence regarding selection of techniques for the suppression of Legionella in water supplies of hospitals and other healthcare premises. their point 12 states: “a system dependent on copper / silver ionisation supplying water at relatively low temperature could provide ideal Legionella multiplication conditions if the ionic concentrations drop below the levels at which suppression is effective. The Response Panel has the concerns that without a high quality feedback control system the copper/silver ionisation or chlorine dioxide systems could lead to a Fail to Danger system”. 

 

How does each system cope with the needs for the wide range of hot water requirements in hospitals?

MYTH:

Hot water is required to be delivered at point of use at a single constant temperature in healthcare buildings.

 

FACT:

Appropriate hot water temperatures need to be delivered for different applications ranging from personal bathing to higher temperature needs such as bed pan washing.

Temperature control systems are designed to cater for these variations in delivering exact point of use temperature requirements whereas ionisation systems will require additional localised point of use water heating or an additional separate system installed to service localised applications requiring hot water at higher than 43oC.

Applications requiring water at less that 43°C will require some form of manual mixing device. The NHS Model Engineering Specification D08 Thermostatic mixing valves (Healthcare premises) specifies four different discharge temperatures for a variety of designations.

Which of the competing systems is 'approved' for use by the Department of Health?

MYTH:

The Department of Health (DH) approve a select number of individual systems or products that can be exclusively used to control the risk of legionella within its property remit.

 

FACT:

The DH lay down comprehensive health and safety standards that any product or system has to meet before it can be installed in any property within its control. To help meet these standards, a series of Hospital Technical Memoranda (HTM) are published by DH and HTM04-01 relates to "The control of Legionella, hygiene, 'safe' hot water, cold water and drinking water systems." Within the scope of HTM04-01 there are clearly defined technical criteria that relate to the effective control of the risk of legionella and these criteria must be met as a minimum by any product or system that is installed in DH buildings. HTM04-01suggests that temperature control is the primary recommended (but not exclusive) method of control in health care properties.Thermostatic Mixing Valves (TMVs) are a mature, proven solution, third party accredited to an NHS Model Engineering Specification and a British Standard. The same cannot be said for ionisation. Ionisation does not appear to have any third party accreditation, Water Regulations Advisory Scheme approval seems to be for materials only. No European Standards are mentioned and the only evidence as to effectiveness is based on manufacturer claims backed up by referenced studies that are many years old.