What is Legionella?

What is Legionella?

Legionella is a Pathogenic Bateria

Legionella Occurs Naturally

What is Legionella?

Legionella is a very serious pathogenic disease - the bacteria are widespread in natural water systems - for example, rivers and ponds.

However, the conditions are rarely right for people to catch the disease from these sources. Outbreaks of the illness more often occur from exposure to legionella growing in purpose built systems where water is maintained at a temperature high enough to encourage growth but not hot enough to kill off the bactieria. 

How do people get Legionnaires' Disease?

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 is between 20°C - 45°C, which encourages growth
• It is possible for breathable water droplets to be created and dispersed in the aerosol created by shower heads, taps and spa baths
• 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
• Outlets are used infrequently
• The system contains dead ends or unused pipe work, e.g. hot water feed for cold fill only machine

Reducing the risk of Legionella

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 so, e.g. on holiday, or there are additional taps/showers/toilets that are not used daily. Good practice in this situation is


• Run the hot water taps (a very unlikely source anyway) for a minimum of 60 seconds
• Flush shower heads for a minimum of 60 seconds, to do this, remove from its holder before turning on the shower, then hold down over plughole to lessen the risk of inhaling sprayed droplets
• Shower heads should be dismantled and cleaned of scale and debris every 3 – 6 months
• Keep the hot water on your boiler system at a temperature of minimum 50°C - 60°C
• Flush the toilet twice to circulate fresh water through the system and empty the cistern


 Maher Ross are qualified Legionella Risk Assessors and we are committed to undertaking a programme of professional Risk Assessment for Legionella across all of our Residential and Commercial properties.  Our Property Manager, Paul Brewster takes about an hour to inspect a straight-forward property and to report on any risks.  During this process, he needs access to inspect the pipe-work, water system and boiler also to measure the temperature the water achieves at the taps and shower heads.

If you need any further information on Legionella, please contact Paul in the Maher Ross office on 01983 563000.