Legionella

The bacteria associated with Legionnaires’ disease 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 domestic hot and cold water systems.

If conditions are favourable, the bacteria may grow increasing the risks of Legionnaires’ disease.

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.

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. For example:

• the water temperature in all or some parts of the system is between 20°C and 45°C
• breathable water droplets can be created and dispersed, for example aerosol created by shower heads, water outlets, spa baths
• water is stored and/or re-circulated
• there are deposits that can support bacterial growth, for example rust, sludge, scale and organic matter
• outlets are used infrequently
• the system contains dead ends or unused pipe work.

The risk of Legionella causing illness in small domestic properties is exceedingly low.

Possibly the biggest risk is when you have been away from the property for more than a week or there are additional taps, showers or toilets that are not used daily.

Good practice in this situation is simply:

• Run all the taps and shower heads for at least 60 seconds every week to make sure you don’t have water standing still in pipes.
• Showers heads and taps should be cleaned of scale and debris every three to six months.
• Keep the hot water on your boiler system at a temperature of minimum 50°C to 60°C.
• Flush the toilet twice weekly with the lid down to circulate fresh water through the system and empty the cistern.
• Report any problems you may have with your hot water system as soon as possible.
• Disconnect and empty any hosepipes when not in use.
• If you have a water butt, items that create spray should not be attached to them.

Warning: beware of scalding!