What is Legionella?....
Legionellosis is a collective term for diseases caused by legionella bacteria including the most serious Legionnaires’ disease, as well as the similar but less serious conditions of Pontiac fever and Lochgoilhead fever. Legionnaires’ disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. The risk increases with age but some people are at higher risk including:
- people over 45 years of age
- smokers and heavy drinkers
- people suffering from chronic respiratory or kidney disease
- diabetes, lung and heart disease
- anyone with an impaired immune system
The bacterium Legionella pneumophila and related bacteria are common in natural water sources such as rivers, lakes and reservoirs, but usually in low numbers. They may also be found in purpose-built water systems such as cooling towers, evaporative condensers, hot and cold water systems and spa pools.
If conditions are favourable, the bacteria may grow increasing the risks of Legionnaires’ disease and it is therefore important to control the risks by introducing appropriate measures outlined in Legionnaires' disease - The Control of Legionella bacteria in water systems (L8).
Where does it come from?Legionella bacteria are widespread in natural water systems, e.g. rivers and ponds. However, the conditions are rarely right for people to catch the disease from these sources. Outbreaks of the illness occur from exposure to legionella growing in purpose-built systems where water is maintained at a temperature high enough to encourage growth, e.g. cooling towers, evaporative condensers, hot and cold water systems and spa pools used in all sorts of premises (work and domestic).
How do people get it?People contract Legionnaires’ disease by inhaling small droplets of water (aerosols), suspended in the air, containing the bacteria. Certain conditions increase the risk from legionella if:
- the water temperature in all or some parts of the system may be between 20-45 °C, which is suitable for growth
- it is possible for breathable water droplets to be created and dispersed e.g. aerosol created by a cooling tower, or water outlets
- water is stored and/or re-circulated
- there are deposits that can support bacterial growth providing a source of nutrients for the organism e.g. rust, sludge, scale, organic matter and biofilms
What are my responsibilities as a landlord...
Organisations, or self-employed individuals, who provide residential accommodation or who are responsible for the water system(s) in their premises, are responsible for ensuring that the risk of exposure to legionella in those premises is properly assessed and controlled. All water systems require an assessment of the risk which they can carry out themselves if they are competent, or employ somebody who is.
In most residential settings, a simple assessment may show that the risks are low and no further action may be necessary. (An example of a typical lower risk situation may be found in a small building (eg housing unit) with small domestic-type water systems, where daily water usage is inevitable and sufficient to turn over the entire system; where cold water is directly from a wholesome mains supply (no stored water tanks); where hot water is fed from instantaneous heaters or low volume water heaters (supplying outlets at 50 °C); and where the only outlets are toilets and wash hand basins). If the assessment shows the risks are low and are being properly managed, no further action is needed but it is important to review the assessment regularly in case anything changes in the system.
Simple control measures can help control the risk of exposure to legionella such as:
- flushing out the system prior to letting the property
- avoiding debris getting into the system (eg ensure the cold water tanks, where fitted, have a tight fitting lid)
- setting control parameters (eg setting the temperature of the calorifier to ensure water is stored at 60°C)
- make sure any redundant pipework identified is removed.
Where showers are installed, these have the means of creating and dispersing water droplets which may be inhaled causing a foreseeable risk of exposure to legionella. However, if used regularly (as in the majority of most domestic settings) the risks are reduced but in any case, tenants should be advised to regularly clean and disinfect showerheads. Instantaneous electric showers pose less of a risk as they are generally coldwater-fed and heat only small volumes of water during operation.
It is important that water is not allowed to stagnate within the water system and so there should be careful management of dwellings that are vacant for extended periods (eg student accommodation left empty over the summer vacation). As a general principle, outlets on hot and cold water systems should be used at least once a week to maintain a degree of water flow and minimise the chances if stagnation. To manage the risks during non-occupancy, consideration should be given to implementing a suitable flushing regime or other measures such as draining the system if it is to remain vacant for long periods.