Decon Pete – legionella and the potential risks

decon peteWith a rise in legionella deaths as services restart, Pete Gibbons explains how dental practices can safely reopen.

In last month’s article I discussed the importance of water quality and the potential risks of legionella. There have been several incidences, lately, that have featured in various media forms detailing outbreaks of this potentially life-threatening decease.

A maternity ward at Darlington memorial hospital shut down the use of its showers due to elevated levels of legionella. Four people died in Ireland from a street cleaning machine. One person died at home from a hose pipe. And two died, along with 22 infected, at a warehouse supplying a cross section of goods including hot tubs.

What is legionella?

For those who aren’t aware, legionella is a very common bacteria found in all water. But it’s particularly prevalent in areas of slow moving or stagnant water.

The HSE issues a document called L8 ACOP, which all dental practices should have a copy of. This document outlines what we need to have in place to mitigate the risks associated.

Ever since the outbreak of COVID-19 and particularly the introduction of the UK’s first national lockdown, dental practices have not been working at their full capacity. In order for dentistry to re-open, back in July 2020, practices implemented a specific list of COVID-safe protocols.

Changes in fallow time

We suddenly saw that many practices saw a reduction in operational surgeries to carry out procedures, during fallow time, safely.

The NHS COVID guidance document, from January 2021, introduced updated information regarding the reduction of fallow times. In particular regarding air changes per hour, which have helped increase the flow of patients seen.

The UK has now entered a state of fully re-opening the country as the vaccination program has been rolled out. Although dentistry is seen as high risk when related to the wearing of face masks, this has meant that more and more patients are able to be seen.

With this we see many once redundant surgeries, being re-opened to be used as originally intended.

After not using these surgeries for some time, we should take some cautionary steps to ensure that they are fully safe and legionella free.

Before using the treatment centre, I suggest running through a biofilm remover to ensure that you have no growth within the tubing.

Regarding hot and cold-water taps, run the cold tap for one minute. Ensure that the temperature doesn’t go above 20c. Run the hot tap for two minutes and ensure that the temperature doesn’t drop below 50c.

Legionella, if present, will grow at temperatures of 22c–45c. So it’s important that hot and cold-water supplies are providing water outside of this temperature.

If you feel that you may have a legionella risk or it is worrying you, then the use of a Point of Use filter will help mitigate any risks.

Reopening surgeries

If your practice is still using a surgery, for the donning and doffing of PPE, then the Department of Health have issued some further guidance to help, which you can find here: www.gov.uk/government/publications/dio-technical-guidance-documents/water-hygiene-guidance-for-buildings-or-sites-closed-or-subject-to-reduced-occupancy-accessible-version.

This outlines the following:

  1. If the building is still partially in use take additional measures to keep the remaining occupants safe
  2. If possible, drop stored water levels in tanks to maintain less than 24 hours storage
  3. Flush to simulate use – weekly flushing may not be sufficient
  4. Monitor temperature to ensure you control any thermal gain in cold water
  5. Consider temporarily increasing levels of potable water treatment dosing – consider other consequences of this such as corrosion and make the decision on balance of benefit
  6. If you lose controls (temperature, biocide levels, etc) the guidance in HSG274 is to sample for legionella weekly
  7. Consider other short-term measures to keep remaining occupants safe. Such as point of use filters at designated locations with other areas shut off.

It’s important to take every precaution possible to mitigate the potential risk of not only legionella, but all water borne pathogens.


If you need any help or assistance please do not hesitate to get in tough with me at www.deconpete.co.uk or email [email protected].

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Catch the previous Decon Pete columns:

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