Legionnaires’ Disease

Legionnaires’ Disease

There are a number of important Health and Safety matters which must be considered when undertaking a Survey. Obviously gas and electrical safety are well known issues and it is likely that water safety will become more important over coming years.

It is often the case that cold water header tanks (often located in the loft) have no covers or poor covers and as a result it is highly likely that many older water heating systems will have unclean water in the hot tanks.

The age and condition of cold tanks is covered in our house and flat Surveys. We look at the adequacy of the support for tanks, the covers, lagging and overflow pipes.

There are also risks of Legionnaires disease in some properties and it is important that facilities such as spa baths be sterilised and flushed using hot water on a regular basis.

The following information was taken from the Health and Safety Executive Website. See:


‘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.

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).

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’

In light of the above and other possible water-related health problems it is important to maintain and improve the water pipes leading into the house, internal fixtures and fittings etc.

Careful attention must be paid to water storage tanks and any old tanks will probably need to be replaced. Spa baths present a particular risk and it is important that such fittings but also showers be regularly flushed with very hot water. It is also possible to arrange for a water system to be sterilised by a qualified plumbing contractor who has the experience and qualifications to sterilise a water system.