Legionella - the danger in still water

7th of March 2014
Legionella - the danger in still water

Maintaining a clean, safe water supply is essential in every built environment.  One of the major threats to the water supply is the legionella bacterium, which can occur in systems that are not adequately protected from it.  Gary Nicholls, managing director of Swiftclean Building Services in the UK, explains the principles of good legionella control.

Controlling and eliminating legionella from water supplies is one of the key tasks of any building manager.  Not only is legionella control good practice; for the responsible person for each property, keeping legionella at bay is a legal duty. Directive 2000/54/EC of the European Parliament and the Council dated September 18 2000, on the protection of workers from risks related to exposure to biological agents at work, categorises legionella pneumophila as a species capable of causing human diseases and therefore lays a responsibility on building owners and managers to prevent this.

There are also two EU Directives which require the safeguarding of the purity of drinking water and bathing water, and while legionella is not specifically mentioned in these, it is widely accepted as one of the major waterborne hazards throughout Europe. In some European countries, legionella has been specifically incorporated into health and safety legislation, among them the UK, where legionella control is covered by Health & Safety at Work legislation and
Control of Substances Hazardous to Health regulations.

Best practice for legionella management is advisable in every region where legionella is a known threat to health.  Failure to exercise effective legionella control frequently has legal consequences, especially in the case of an outbreak of legionella.  For most fit adults, legionella produces a debilitating illness which resembles influenza; for the elderly, the infirm or the very young, it can prove fatal.  In these cases, both the organisation and the individual person responsible for the property may face prosecution and, in the case of related deaths, potential imprisonment for failing to prevent a legionella outbreak.

Throughout much of Europe, water systems for larger properties typically include communal water tanks situated on the roof, in order to make best use of the space available. In cold weather, when water temperatures are generally well below 20°C, there is little threat from legionella bacteria.  In warmer months, however, the enclosures in which water tanks are situated often retain heat and cause the water temperature levels to rise.

Once it reaches temperatures in the range of 20°C - 45°C, water also fulfils one of the prime conditions to foster the growth of legionella and begins to represent a potential health hazard. Where possible, the water temperature should be controlled, therefore, either by actively cooling the water, or by insulating it against temperature changes outside the building, so that the water temperature does not achieve levels within the hazardous range.

The condition of the tanks themselves is also critical. Where tanks have become rusty or their surface is no longer sound, they may need renovation or replacing.  Tanks can also be prone to the ingress of vermin, so any debris must be removed and the means of access for insects, pigeons or rodents blocked and secured.  A sound, clean tank is essential for healthy water storage, so any dirt must be removed; the tank being effectively cleaned and sanitised before refilling.

Water is more likely to foster legionella if it is static. Buildings such as manufacturing facilities and educational establishments, which have shutdown periods of one or two weeks or more are at greater risk, as it means that water stays static in pipes and tanks for prolonged periods. The danger, ironically, frequently occurs when attempting a deep clean prior to reopening the property again after the break.

Many organisations choose the period just before reopening to perform a thorough clean in order to provide a clean environment for the occupants; employees, teachers or students.  For this, water is needed. Typically, cleaning teams will perform the cleaning after the water has been static for ten days or more, so that legionella has had a good chance to breed; especially during a warm summer vacation.

If there is a legionella outbreak, the first people to be subjected to legionella bacteria will therefore be the very people trying to provide a clean environment; the cleaners.  As there is a three week incubation period for legionella, they may well be infected before the outbreak is discovered.

Vulnerable to infection

Despite the deep cleaning process, those returning to use the building will also be vulnerable to infection, the first cases not being reported for some time.  In a property which has a lot of outside visitors, the scope for the contraction of legionnaires disease could be extensive.  For this reason, the domestic water supply needs particular care during shut downs.

Regular flushing of little used outlets is the best defence. Flushing the water through taps, shower heads and drinking fountains not only creates movement of the water through the system, it also helps to keep the temperature lower as the water in the tanks is replenished by fresh water entering the tank at a lower temperature.

In multiple occupancy residential buildings, such as apartment buildings and care homes, it is important to treat individual rooms with basins or en-suite bathrooms in the same way, regularly flushing water though basins, baths or showers if a resident is away for a vacation or a stay in hospital. In public housing situations, tenants should be issued with advice to this effect and advised to flush their water systems thoroughly on their return from periods away from home.

Regular flushing is also important advice for hotels, hospitals, dental care establishments, veterinary practices, beauty establishments and leisure facilities in which rooms supplied with water go unused for periods of several days.

Some older water systems were designed at a time when there was less awareness of the risks associated with legionella. Others may have had their water systems changed due to renovation or extension. In these cases, stretches of pipework known as ‘dead legs’ sometimes occur. These are ends of pipework which are no longer, or very seldom, used.   Although smaller amounts of water are trapped here, the small body of water is nonetheless static and can form a breeding ground for legionella bacteria, which can then spread.

Some parts of the system may no longer be necessary. This may include outdoor taps which are no longer required, or a dead end in the pipework, where a bathroom has been moved but not all the now unnecessary pipework has been dismantled. In these instances, dead legs in the pipework can simply be removed so that the water in the system as a whole is generally circulating on a regular basis through every part.

Identify the risks

The first step in the control of legionella is to appoint a responsible person for each building. In many countries this is a legal responsibility; in every country it is good practice. This person should then be responsible for ensuring that a number of measures are carried out. They should either be well trained in legionella control or they should employ an outside specialist in order to ensure that they fulfil their responsibilities. The legal consequences of not achieving compliance with legionella regulations are frequently serious, and can include facing criminal charges, so they may need to rely on expert advice.

Once the responsible person is appointed, they must ensure that a risk assessment of the entire water system for both drinking and bathing water is in place, the same applies to systems with water used in water features. If this has not been done before, it must be completed, but if the responsible person is taking over the duty from someone else, they should make sure that the risk assessment is already in place and is reviewed regularly.

Carrying out a risk assessment involves inspecting and observing the condition of each part of the system, determining how water is used and the pattern in which it is used. It should cover how water is stored, where it flows, how it is delivered at each point of use and whether there are long periods during which it is not used. This is why bringing in specialist help may be advisable. The risk assessment must be carefully documented.

A schedule should be drawn up of any remedial work that is needed to bring the water system up to the required national standard. This will help to ensure, with careful maintenance, that it stays legionella free. The system should be tested to determine whether it is free from legionella and treated to eliminate it if necessary. Intervals at which a system should be tested may vary from country to country. In some, testing at set intervals may be required, while others may only require retesting if a significant change has been made to the water system since it was last tested and assessed.

Our own recommendation is that the system should be reviewed on at least an annual basis to establish whether anything has changed and whether any problems have been reported. It may also be wise to check for undue sickness levels in the occupants of the building.  This last measure may also indicate other problems, so is well worth considering.  If there is any cause at all for concern, we would recommend testing for the presence of legionella.

Regular temperature testing, cleaning and flushing should be sufficient to keep water systems free from bacteria, but if there is unusually hot weather, we would recommend being extra vigilant. A legionella control expert will be able to help you to establish the routines that will keep legionella outbreaks at bay in each individual building.

Keep records

The duties of a responsible person are substantial; so it is best practice, as well as frequently being a legal requirement, to keep accurate documentation which demonstrates the anti-legionella measures which have been taken.

We recommend the UK system of log books as these carefully document the precautions taken, the testing undertaken and remedial work done. They also provide clear information which helps to safeguard the responsible person and provide some protection from prosecution in the event of an unexpected legionella outbreak. Online record keeping is the modern method being used by many responsible.

While keeping a pristine built environment is often a matter of pride, excellence and customer satisfaction, keeping legionella at bay is even more critical than this.  In a legionella control process, it pays to bring in a niche specialist cleaning provider, who will help to ensure the wellbeing of the cleaning team itself, as well as all its customers.

In the final analysis, vigilant and meticulous legionella best practice saves lives.



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