Legionella Policy

St Chad’s Legionella Policy

Legionella is a genus of bacteria capable of infecting people after inhalation in water aerosols The diseases caused are known as Legionellosis, the most serious being Legionnaire’s Disease – a form of pneumonia.

The College Policy is to ensure the Health and Safety of College staff, students and others from the risk of infection presented by Legionella bacteria, universally present in water systems, and to implement the standards of HSE Approved Code of Practice (L8), so far as is reasonably practicable.

Responsible Officers

College Principal

College Bursar

Clerk of Works


Risk Assessment

To present a risk, a water system must have:

  • Water at temperatures between 20 to 45 degrees C
  • A nutrient supply.
  • Areas of stagnation.
  • Dispersal in a respirable aerosol/spray
  • People present within the vicinity.

Such situations may include water-cooled cooling towers, evaporative condensers, industrial sprays, showers and air conditioning plants, or places where spray could be generated during the cleaning, repair and maintenance of the system.

Concerning risks to people, age group and sex are important factors:

  • Legionnaires’ Disease mainly affects people in older age groups.
  • Men are about three times more likely to be ill than women.
  • Young families are less likely to be at risk.
  • The disease is almost unheard of in children.
  • Smokers are at a higher risk of the disease than non-smokers.


Complete avoidance is not reasonably practicable in listed buildings where water pipes were installed and building construction taken place in an ad-hoc manner. Therefore, a system of checking, inspecting and monitoring must be implemented.

The results must be:

  • Recorded in writing.
  • Retained for at least 5 years.
  • Signed


Risk controls – General

The primary objective is to prevent Legionella proliferating in water systems and to avoid the creation of water sprays and aerosols. These should include:

  • Controlling the release of water spray
  • Avoiding water temperatures between 20 and 45 degrees Celsius.
  • Avoiding water stagnation.
  • Avoiding the use of materials that may harbour or provide nutrients for bacteria and other micro-organisms
  • Keeping the water system and the water clean
  • Use of water treatment techniques – e.g. chemical and thermal disinfection; biocides

Risk Controls – Specific

  1. During the day and evening, hot water temperatures are kept at levels that help to prevent legionnaire’s disease. This slightly increases the danger of scalding, but it greatly reduces the risk of legionella colonisation. Many of the boilers have a once-weekly legionella cycle that increases the domestic hot water temperature for a time precisely to destroy this bug.
  2. Cold Water tanks are treated annually with chlorinated products to destroy this bug.
  3. The Hot Water system is checked on a quarterly basis to ensure that the temperatures at both sentinel and representative taps (n.b. all taps in St Chad’s are treated as sentinel taps) is at least 500 C after running for 1 minute.
  4. The boilers are checked annually to ensure that the flow temperature is 600 C and the return temperature at least 500
  5. Cold Water temperatures are checked on a quarterly basis to ensure that the temperature is below 200 C after running for 1 minute.
  6. Shower heads are removed and replaced and then dismantled, cleaned and descaled on a quarterly basis.
  7. When showers are out of use for a period of over two weeks they are flushed-through before further use.

28 February 2014