Getting to grips with Legionella

We speak to Lucy Foord, practice support manager at DBG, about Legionella and why it’s imperative to understand more about the bacteria and the risk it poses to your patients.

Legionella isn’t the sexiest of subjects, I agree, but the more you know about the bacteria and waterline management the easier it will be to manage the risk and protect your patients.

It’s believed that Legionella was first discovered in the 1970s in Philadelphia after an outbreak of pneumonia occurred in visitors to a state convention of the American Legion. Subsequently the illness became known as Legionnaires disease.

  • Since January 2017 there have been 286 cases of Legionnaires disease reported to the national surveillance scheme (i)
  • 74 of the cases were reported in the month of June 2018 (ii)

Legionella is a gram-negative bacterium that is normally and most commonly found in water and waterlines. Legionella bacteria will multiply in water temperatures between 20 degrees Celsius and 45 degrees Celsius. Equally, it will lay dormant in water below 20 degrees Celsius - but will not survive in water above 60 degrees Celsius.

Risk management
Water needs to be checked by a competent person regularly to ensure it meets the set requirements and is not harbouring the bacteria.

The outlets closest and furthest away from every tank or cylinder should be identified. These should be checked once a month for temperature control - ensuring the water is below 20 degrees Celsius for cold outlets and above 50 degrees Celsius for hot outlets.

You must also test your hot water tank monthly to ensure it is above 60 degrees Celsius. And your cold-water tank must also be checked at least every six months to ensure the water is stored below 20 degrees Celsius. Documenting all these steps are a must too.

It’s important to remove any dead leg pipes you have as legionella bacteria loves to grow in stagnant water. And it is advisable that all low use outlets, such as taps and showers, are flushed for a few minutes every week.

Dental unit waterlines must be well managed. Patients consume this water – regardless of how good your aspiration skills are – and it will be going into open wounds and surgery sites. The bacteria in water lines can cause disease such as Mycobacteria and Pseudomonads. Water companies must ensure that they keep below the limit of 100 Colony Forming Units (CFU). These bacteria form biofilms which is what we as dental professionals are trying to reduce in our water lines by using products designed for this - although there is not one on the market yet that removes 100 per cent of biofilm.

It is important we use either sterile bottled water or reverse osmosis water in dental unit water lines too. If tap water is used there is a chance of introducing opportunist respiratory bacteria into the lines which cause biofilm to form.
Waterlines should also be purged at the start of every session for 2/3 minutes and for 20/30 seconds between each patient as well. All units should now be fitted with anti-retraction valves as per EU regulations.

Although the whole team is responsible for maintaining the waterlines, HTM 01-05 states that under the Health and Safety at work Act 1974, it is the registered manager who must take responsibility for ensuring all the above are carried out. Health and safety risk assessments should be carried out to ensure compliance and that regulations are being met, this can be organised through the DBG.

A recap of the mandatory requirements

  • All systems require a risk assessment, however not all systems will require elaborate control measures.
  • All premises are required to have a written waterline management scheme and legionella risk assessment. These schemes should be written by experienced and competent people. A competent person is someone with the necessary skills, knowledge and experience to carry out this function.
  • The registered manager must ensure that all the recommendations of the written scheme and risk assessment are implemented.
  • Water and air lines must be fitted with anti-retraction valves in accordance with EU regulations.
  • It is mandatory to control Legionella within the dental waterline system, but there is no one single system of treatment which is 100 per cent effective.

To make sure your teams are correctly trained in what Legionella is, where it comes from and how it can be prevented, just contact the DBG on 0800 028 1697.

Alternatively, do you need a Legionella risk assessment? DBG, in partnership with global water management specialist, Euro Environment, work to ensure dental practices meet the legal requirements. As part of the assessment each dental practice will be surveyed by Euro Environmental and in accordance with the Approved Codes of Practice L8 document, HTM 04-01 and HTM 01-05. For more information call 0800 028 1697.


(i) Legionnaires’ disease monthly surveillance reports: 2018
(ii) Legionnaires’ disease monthly surveillance reports: 2018