The latest Code re-emphasises the importance of the management of water hygiene. The document combines the revised 1995 edition of the Code with the revised associated technical guidance note, HS(G)70.
The Water Management society has also helped by introducing a voluntary Code of Conduct for its water treatment members and others involved in dealing with legionella. This explains to clients what they may expect from companies who adopt the Code. Some 50 companies are reported to have already accepted it.
So what does the latest Approved Code of Practice require?
Essentially, the Code retains the three traditional control techniques for legionella, namely:
- cleanliness to limit the nutrient available
- avoidance of stagnation to limit the time for multiplication of legionella
- keeping the water properly hot or cold to limit the speed of multiplication of the bacteria. Where water remains lukewarm in the danger zone of 200C to 500C for some hours, then biocidal treatment is necessary
The Code welcomes novel methods of control, particularly for systems which find it difficult to meet the conventional thermal control methods. However, proof of success of such new methods is required.
The major changes
There are a number of important changes. The management of water hygiene is now seen to be one of controlling the microbiological risk, rather than minimising it.
All services providers and water treatment specialists are now required to be effective, and as part of this they are being encouraged to define how they might work more closely and effectively with their clients. This requires written agreement of how the responsibilities for compliance may be shared – but not delegated – by the employer.
More maintenance and testing detail is provided, and crucially, the Code now requires that cooling tower water be tested for the presence of legionella.
The size limitation for excluding smaller domestic hot water tap systems has been removed. Originally, hot water systems below 300 litres were excluded from the risk assessment. In future, all hot water systems will be included. Whirlpool spas are given more emphasis in the light of major outbreaks of legionnaires' disease outside the UK.
Testing issues
There are still wide differences between countries on the issue of testing for legionella. However, the response from the public consultation stage of the draft Code was very strongly in favour of such testing.
There is no known relationship between outbreaks of legionnaires' disease and the concentration of legionella in offending water systems. However, it is reasonable to suppose that the risks increase with the rise in contamination.
The real epidemiological link is between outbreaks and neglected water systems. However, as modern biocide techniques are designed to eliminate the legionella, testing is now accepted as evidence that a water treatment regime for a tower is working as intended.
The criterion for detecting legionella in normal water samples is 100 colony-forming units per litre. If an occasional water sample shows a higher value, then a repeat measurement is needed. If the values are significantly higher, then immediate action is required (table 1). Other bacteria can be tested weekly using a dip-slide. More guidance on recommended inspection and cleaning intervals are given in table 2.
One dramatic surprise came out of general discussion at the HSE's Legionella Conference at the end of October. Environmental Health Officers are now obliged to close down all evaporative cooling towers in the area of any outbreak while they seek to identify the cause.
This is a very important issue. Many new air conditioning installations serve computer suites and provide the necessary close temperature control. The cost of switching off such units could be drastic for such a company and would incur severe financial penalties. Motivation for such designers to opt for a dry tower will be high as they are immune from the legislation.
Note that the CIBSE's revision of its own legionella guidance TM13 has also been published. The CIBSE worked in close co-operation with the HSE during its creation , and the two documents are compatible.
The new Code – with its associated guidelines – will be available at the end of December.
Background to the Code
Health and safety investigations into the growth of legionnaires’ disease epidemics in the mid 1990s, showed that many cooling towers failed to comply with the Approved Code of Practice (ACOP). This prompted an HSE survey of how well the HSE’s Code was being implemented in practice. The national survey between 1997 and 1999 took in 600 premises with cooling towers. Investigators found that tower cleaning, water treatment and monitoring of water quality was carried out well, but that the water management was poor. For example, the HSE inspectors had difficulty in getting access to almost half of the towers. Around a third of companies had not identified the manager responsible for water hygiene, nor had they undertaken a risk analysis of their water services. Less than half had a defined contractual responsibility of their water services. Around 60% of the companies surveyed subsequently received letters from the HSE. 153 improvement notices were served and 22 prohibition notices.Source
Building Sustainable Design
Postscript
Dr Geoffrey Brundrett FCIBSE Hon FRSH is a past-president of the CIBSE and currently executive chairman of the Royal Society of Health. He was chairman of CIBSE TM13, and sat on the drafting panel for the HSE Approved Code of Practice.
