Legionella control
Everyone will recognise the dangers of Legionnaires' disease, which was first discovered in 1976 at the Bellevue Hotel, Philadelphia, where more than 200 people became ill with a mystery lung infection. Thirty-four of these people subsequently died. Because the persons infected were delegates at a conference of American Legionnaires the infection was named Legionnaires' disease. It was later recognised that cases of the disease had been occurring from the end of the Second World War.
In 1985 175 patients were admitted to Stafford district hospital with chest infections; a total of 28 people died. Outbreaks have continued to the present day throughout the world - RAH Consultancy was involved in a case of Legionnaires' disease that occurred in an Egyptian hotel.
Legionella pneumophila is a common source of Legionnaires' disease and 35 serotypes (variations) of the bacterium have been described. The bacillus (a rod-shaped microbe) is a frequently occurring organism found naturally in soils and water systems. Although the majority of incidents have arisen from cooling towers and air conditioning, they also occur regularly through badly maintained and designed water systems. Legionella thrives in water in the temperature range of 20 to 45 degrees Celsius.
Below 20 degrees Celsius the bacillus is dormant; prolonged exposure to temperatures around 60 degrees Celsius will destroy the bacteria, but the length of exposure required to destroy them depends on the density of the population.
The Health and Safety Executive (HSE) considers temperature control as the primary method to limit the risk of Legionella infections from water systems.
There are numerous claims that other methods of control are equally as effective, but I believe personally that these claims need to be treated with care. It is relatively easy to check that the hot water has reached an effective temperature. Thermometers can be placed at strategic points upon a water system and the resulting temperature noted.
Systems such as copper/silver ionisation or chlorine dioxide dosing are not so readily monitored. The Water Supply (Water Quality) Regulations 2000 and their amendments strictly prohibit exceeding the maximum values for substances within the water supply, such as copper or silver.
With regard to chlorine dosing, the free residual chlorine should be between 0.2 and 0.5 milligrams per litre, and the presence of top-up dosing systems within the water system can affect this free residual level. Dosing pumps need to operate while water flow is occurring and not continue dosing during periods of stasis.
A further common disinfection system, that of UV radiation, also has its disadvantages. Most significantly, it has no residual effect: if bacteria are present in the water system downstream of the device the treated water will be recontaminated.
The Water Byelaws 1989 and their successor, the Water Supply (Water Fittings) Regulations 1999, are very specific about maintaining the temperature of hot water services at a suitable level. The Department for Environment, Food and Rural Affairs' guidance note to schedule 2, section 8, paragraph 18 of the Water Regulations (G18.2) states: 'Hot water should be stored at a temperature of not less than 60 degrees Celsius and distributed at a temperature of not less than 55 degrees Celsius. This water distribution temperature may not be achievable where hot water is provided by instantaneous or combination boilers.'
The NHS reinforces this position in its own internal guidance documents and the HSE code of practice and guidance 'Legionnaires' disease: The control of legionella bacteria in water systems' must be applied to those areas where the Health and Safety at Work Act 1974 applies.
Essentially, all the guidance for both domestic and commercial hot water systems requires the maintenance of the hot water temperature as the major control mechanism for the control of Legionella.
Scalding: The dangers
Unfortunately, in the effort to limit the growth of Legionella the hot water system becomes a risk to people's health due to the danger from scalding. Everyone using hot water systems must be presumed to be potentially at risk.
Dr JP Bull, when researching for the industrial injuries and burns unit of the Medical Research Council, carried out work to illustrate the time and temperature relationships which result in partial and full thickness burns. The work was carried out on human cadavers, and therefore the time/temperature relationship was based on observing the skin damage and cannot relate to the pain threshold. Nevertheless, his figures show that at 60 degrees Celsius partial thickness burns will occur within approximately seven seconds, and at 70 degrees Celsius within one second.
However, both the young and the elderly have much thinner skin than a healthy adult, and this raises the risk dramatically. For instance, the Coffee Council (in an article from 2010) stated that in the UK more than 15,000 children are scalded by hot beverages each year, and 1,100 of these children require major treatment.
Netmums suggests more than 100 people attend accident and emergency departments each day with a scald or burn injury. A liquid at 60 degrees Celsius will cause burns after three seconds on a child or elderly person. A campaign called 'Hot water burns like fire' points out that a scald of more than 20 per cent of the body, not uncommon if a small child falls into a bath of hot water, has the same impact as being 'hit by a bus'.
Despite major campaigning by governments and NGOs, scalding incidents for children associated with tap splash, spillage, or bathing immersion averaged more than 250 cases every year from the start of the millennium. In 2012 3,951 children under the age of five were so badly burnt that they were put under specialist treatment.
I personally was involved in investigating the issues arising from a scalding case where a child was badly scalded on the chest and hand after falling into the hand wash basin. The child, who was less than three years old at the time, will probably still be undergoing treatment until he is fully grown, and possibly longer. The unfortunate thing is that temperature control devices were not then obligatory.
Thermostatic mixing valves (TMVs)
The whole point of this article is to inform readers of the steps that responsible installers and users of hot water systems should be undertaking to limit the public's exposure to scalding injuries.
This article will concentrate on washing and whole body immersion, and the use of TMVs in limiting point of use hot water temperature.
In my view, the most effective measure to prevent scalding is by limiting the outlet temperature of the hot water. The most effective device to limit the temperature of this water is a thermostatic mixing valve (TMV). These devices mix the hot and cold water in the body of the valve and emit it at a lower and safer temperature for bathing. In 1998 the NHS recognised the necessity of this approach and produced the health guidance note 'Safe hot water and surface temperatures'.
It recommended that there are three types of mixing valve: a mechanical mixing valve or tap, wherein the water temperature is physically controlled by the operator (type 1); a TMV complying with the present British Standards Institute BS EN 1111 and 1287 requirements (type 2); and finally a TMV with enhanced thermal performance complying with NHS model engineering specification D08 on TMVs installed in healthcare premises. These standards are applicable to all healthcare premises and those premises registered under the Registered Homes Act 1984. The 'safe' hot water guidance note is the primary guidance available.
In order to certify valves to meet this requirement, the TMV3 accreditation scheme was initiated by Buildcert, and to this day this programme is used to test and certify these valves. The certification includes ongoing audit testing of the valves.
The TMV3 approval guide laid down maximum hot water temperatures for each of a number of washing and sanitary devices. The recommendations for the maximum set hot water temperature are:
• 46 degrees Celsius for bath fill (for assisted bathing only - bathrooms operating baths at this temperature should be made unavailable to unaccompanied bathers);
• 44 degrees Celsius (for unassisted bathing);
• 41 degrees Celsius for showers;
• 41 degrees Celsius for washbasins; and
• 38 degrees Celsius for bidets.
Temperatures should never exceed 46 degrees Celsius.
The guidance states that valves certificated to TMV3 should be used on bidets, showers, wash basins, and baths for young, elderly, and disabled people who may be at risk.
In writing the safe hot water temperatures guidance and producing D08 a commitment to a mutually supportive engagement was required. In order to guarantee that the valves will remain effective they need to be properly designed, correctly installed and commissioned, and regularly monitored and tested. There therefore exists this bond between the manufacturer, the plumber/engineer, and the hospital maintenance department.
It is important that the valve be installed in a system where the limits of operation are known. They operate across two pressure ranges: a low pressure system (0.2 to 1 bar) and a high pressure system (1 to 6 bar). Valves which are able to operate across both of these ranges separately are available, but it has to be understood that these valves are unable to operate across the two ranges with, for instance, a 0.2 bar cold supply and a 6 bar hot supply; either the hot supply would have to be reduced via a pressure reducing valve, or the cold supply would have to be boosted via a pump.
Similarly, the hot supply and the cold supply are restricted to 5 to 20 degrees Celsius for cold water and 52 to 65 degrees Celsius for hot water. This is particularly important for the hot supply used with baths, as the hot temperature acts as the 'engine' for powering the valve and the differential between the minimum value of 52 degrees Celsius and the 46 degrees Celsius maximum outlet temperature of the valve only provides a 6 degrees Celsius variance to operate the fail-safe closure of the valve quickly enough.
Valves installed on water systems where the pressure and temperatures vary from the conditions of normal use stated above will not be covered by the certification of TMV3.
Legislation which refers to TMV3 valves includes:
• NHS health guidance note on safe hot water temperatures;
• Care Standards Act 2000;
• Care Homes Regulation 2001;
• Guidance to the Water Regulations (G18.6);
• HSE 'Health and safety in care homes' guidance; and
• Children's Homes Regulations 2015 and the School Premises Regulations 2012.
The installation of TMV3 certified valves is required by legislation or authoritative guidance at the following premises:
• For baths, basins, and shower usage in young person's care homes and NHS hospitals;
• For use with showers and baths (at a maximum temperature setting of 43 degrees Celsius) in schools for severely disabled children, including nurseries;
These valves are recommended by legislation and authoritative guidance:
• For baths, basins, and shower usage in NHS nursing homes, private nursing homes, and private hospitals;
• For hand washing in schools for severely disabled children, including nurseries.
All of these devices should be installed, commissioned, and maintained strictly in accordance with the guidance issued as part of the TMV3 scheme certification. Here lies the rub, as in not all circumstances are the technical abilities of the installers and maintainers up to the levels that the system endeavours to ensure. There is also the consideration of cost: performing adequate levels of maintenance and ensuring that the conditions of use can be met have cost implications. These implications may be serious, but the guidance all points in the direction of using these devices as the primary defence against scalding while maintaining the defence against Legionella.
Adequate documentation is also required to prove that the maintenance activities are carried out. This can easily be done at the same time as the documentation required for the control of Legionella is undertaken.
The list of suitable certificated devices is available on the TMV3 website.
Private dwellings and TMVs
For many years, manufacturers, the Children's Burns Trust, and doctors associations specialising in burns had been concerned about the level of scalding incidents in the home. Of particular concern were the continuing levels of scalding incidents among children.
The Children's Burns Trust, in collaboration with the Bathroom Manufacturers Association, the public health and safety organisation NSF-WRc, and others, had lobbied parliament for a change to part G3.65 of the Building Regulations 2000. After much research into the incidence of scalding, the government decided that the legislation should cover only whole body immersion for bathing and would not legislate for provision of temperature control of hand washing or showering. Nevertheless, this was seen as a big step forward in the prevention of scalding, particularly of children.
The relevant sections of G3 are those paragraphs related to the prevention of scalding (3.65-3.68), which require 'the hot water supply temperature to be limited to 48 degrees Celsius by use of an in-line blending valve or other temperature control device, with a maximum temperature stop and a suitable arrangement of pipework'. The guidance draws attention to the BRE information paper IP14/03 'Preventing hot water scalding in bathrooms: Using TMVs'.
In order to meet the requirements of the legislation, the TMV2 scheme has been promoted. This tests TMVs to the European standards BS EN 1111:1999 and BS EN 1287:1999. The certification scheme also requires that these valves undergo an annual testing regime similar to that required by the TMV3 scheme. These G3 requirements apply wherever the Building Regulations apply:
• The use of these devices is mandatory for housing association dwellings for the elderly;
• They should also be installed for use with showers and baths (at a 43 degrees Celsius maximum temperature setting) in schools, including nurseries;
• They are recommended for hand washing in schools, including nurseries, and for bathing in housing association dwellings; and
• It is best practice to use such devices in all situations in private dwellings and hotels, and for hand washing and showering in housing association dwellings.
46 degrees Celsius is the maximum temperature for water from the bath hot tap, having regard in particular to the margin of error inherent in TMV2 valves and temperature loss in metal baths, especially in cold bathrooms. It is not a safe bathing temperature for adults or children.
The British Burns Association recommends 37 to 37.5 degrees Celsius as a comfortable bathing temperature for children. In premises covered by the Care Standards Act 2000, the maximum water outlet temperature is 43 degrees Celsius.
It is again apparent that this legislation has cost implications and that it relies once more upon the competence of the installers and the continued maintenance of the devices to a reasonable standard of care. Guidance on how this is undertaken forms part of the TMV2 schemes certification. It is small price to pay for reducing the likelihood of child injury.
Investigations into scalding incidents
Where scalding has occurred to anyone within either commercial or domestic premises, my advice is that investigations are undertaken into the presence of anti-scald devices.
The following points need to be considered:
• Have certificated devices of the correct type been installed (TMV3 or TMV2)?
• Are the certificated devices suitable for the application for which they are used, i.e. are they for use with a shower only, with a shower, bidet, or bath only, or for all applications?
• If certificated devices have been installed, are the conditions of use acceptable?
• Have they been correctly installed?
• Have they been correctly commissioned?
• Have they been subjected to the correct maintenance and in situ testing? and
• Do the records of all this activity exist?
If any of these conditions cannot be supported then it is likely that an element of blame can be established.
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Personal experience
Richard Hurst was for many years an employee of the Water Research Centre (WRc). For 15 of these years he was responsible for contract management of all testing outside the remit of the Water Regulations.
In the 1990s the NHS was painfully aware of the frequency of scalding incidents in hospitals and other care establishments. A Scottish newspaper article from this period reported that over 80 deaths from scalding took place in Scottish hospitals alone within a five-year period. One can then extrapolate from this what the figures for the entire UK hospital population would have been.
The NHS attempted to produce a test method to establish the safety and reliability of TMVs. Richard was asked to develop a test protocol to be followed in order to validate the NHS document. His investigation proved that this initial attempt at a standard was impossible to meet and he wrote to the NHS pointing out this result.
As a result, a committee formed by the NHS and manufacturers was established to draft a new industry standard. Richard actively encouraged this work and himself devoted many hours to the project, which resulted in the publication of the safe working temperature standard D08. The launch of this standard in 1988 resulted in the Buildcert certification scheme TMV3, which operates to test valves to this standard.
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Richard Hurst is the proprietor of RAH Consultancy
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