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written scheme for the prevention or control of legionellosis



At Hygeia we take health and safety very seriously and as part of our premises management regime we aim to prevent and/or control legionella risk in accordance with the Health and Safety Executive’s Approved Code of Practice on legionella – “The control of legionella bacteria in water systems” (aka ACOP L8).

Persons with responsibility for the management of legionella risk

The “Statutory Duty Holder” in relation to Hygeia Dental Care’s premises at Malt Mill Lane, Totnes, Devon, TQ9 5NH is Joanne Giddy.  She has overall legal responsibility for the management of legionella risk.

The “Responsible Person” for the purposes of the day-to-day management of legionella risk and, in particular, water systems, is Neil Phillips.  He is responsible for ensuring that:

  • the water system is fit for purpose;
  • the water system is maintained correctly;
  • a Written Scheme is prepared setting out the procedures that must be followed to ensure that legionella risk is minimised;
  • the Written Scheme and the procedures contained in it are kept up-to-date;
  • the legionella risk assessment is reviewed at intervals of 2 years;
  • the legionella risk assessment is reviewed when alterations are made to the water system;
  • the legionella risk assessment is reviewed when there are changes in use of the system or the building;
  • the legionella risk assessment is reviewed when new information about risks or control measures becomes available;
  • the legionella risk assessment is reviewed when there are changes to the results of tests indicating that control measures are no longer effective;
  • the legionella risk assessment is reviewed when there is an outbreak of Legionella associated with the water system;
  • the recommendations in these risk assessments are acted upon;
  • testing and/or monitoring is carried out at appropriate intervals;
  • appropriate training is provided for staff;
  • proper records are kept.

Review of this Written Scheme

This Written Scheme will be reviewed:

  • Annually;
  • On completion of an updated legionella risk assessment (normally biennial, but also includes occasions when significant alterations have been made to the water system or the use of the building).

Specific measures for the control of legionella risk

Based on the guidance set out in ACOP L8 and the risk assessment carried out by an independent expert in April 2011, the following measures are taken in order to minimise and control the risk of legionella at Hygeia Dental Care:

  1. Daily – Dental Unit Water Lines (DUWLs) are supplied from a bottled water system that re-filled with RO water treated with Alpron.  This is drained down at the end of every day and bottles from the system are stored inverted and dry until the following day.
  2. Weekly – “flushing” – the outdoor tap is flushed for 30 seconds (this is the only outlet on the system that might otherwise be unused for extended periods).
  3. Weekly – “routine monitoring” – involves checking that all taps, Thermostatic Mixing Valves (TMVs), toilets and Reverse Osmosis (RO) units are operating, that the calorifier (water heater) and the programmer that controls it are working correctly (NB the system is programmed to operate for 1 hour on days when the practice is not open), that there are no leaks or other obvious damage to the system and that the water runs clear and is odour-free.
  4. Monthly – cold water outlets are tested to ensure that the temperature of the water is below 20 Celsius within 2 minutes (where a TMV is fitted, surface temperature is checked at the valve inlet).
  5. Monthly – hot water outlets are tested to ensure that the temperature of the water is above 55 Celsius within 1 minute (where a TMV is fitted, surface temperature is checked at the valve inlet) – updated January 2016 – previously 50 Celsius within 1 minute.
  6. Monthly – the surface of the outlet pipe on the hot water cylinder is tested to ensure that the temperature is 60 Celsius or higher;
  7. Six-monthly – the temperature of the water in the cold storage tank is tested to ensure that it is below 20 Celsius both at the ball valve inlet and at the far side of the tank.
  8. Six-monthly – TMVs are inspected, tested and maintained as necessary.
  9. Six-monthly – condensate trays in the air conditioning units are cleaned and disinfected.
  10. Six-monthly – an audit is carried out to ensure that the maintenance and monitoring records are properly kept.
  11. Annually – water is drained from the hot water cylinder to ensure that it is clear.
  12. Annually – cold water tank is inspected to check that the lid is in good condition and is a close fit, the insect screen on the overflow is intact, the insulation jacket is in good condition and that the water is clear and free from debris/sediment.
  13. Annually – water usage is checked; this means closing the ball valve in the cold water tank and observing the rate at which the level falls – ideally the amount stored should be sufficient for no more than 24 hours’ use.
  14. Annually – system schematic checked to ensure that it is still up-to-date – if changes have been made then the risk assessment should be repeated.
  15. Annually – the integrity of the system is checked to ensure that it is intact – NB insulation on pipework.
  16. Annually – the site logs are checked to ensure that they are in order – eg that temperature records are complete, that any necessary action has been taken.
  17. Annually – the Statutory Duty Holder and the Responsible Person should undergo legionella awareness training.
  18. Biennially – legionella risk assessment carried out.

Weekly, monthly, six-monthly and annual checks & tasks record sheets have been designed to capture adequate records of these processes and are available from the hygeia document database.

Cleaning and disinfection of cold water storage tanks

In accordance with ACOP L8, the cold water storage tank does not undergo routine cleaning and/or disinfection but only when routine inspections show this to be necessary, significant work has been undertaken on the water system such that might lead to contamination or there has been a legionella outbreak.

Microbiological testing

Similarly, microbiological testing is not routinely undertaken.  It will only be carried out where it is indicated – for example, where water develops an unpleasant odour or taste, where there is a routine failure to meet water temperature targets or there has been a legionella outbreak.

Work carried out on the water system

Where work is carried out on the water system, materials used must not harbour bacteria or other microorganisms nor provide nutrients for bacterial growth.  Correct procedures must also be followed for shutting down the system and for re-commissioning it when the work is complete (see below.)

Shutdown & re-commissioning

To shut down the system, first turn off the water heater using the controls in the office.  The water supply can be turned off at the main stop-cock in the staff room.  If it is necessary to drain the system, the hot water tank can be drained via the drain cock in the cupboard in the office (this will, in turn, empty the cold water tank that feeds the cylinder by gravity).  Taps can also be opened to allow any remaining water in the cold supply system to empty.

To re-commission the system, close the drain cock and all the taps.  Allow time for the cold water tank and hot water cylinder to refill before proceeding any further.  Once the tanks are full, flush all taps in the building for 5 minutes.  Switch the water heater back on.  Allow the hot water cylinder to heat up for 30 minutes.  While this is happening, perform system checks in accordance with the weekly, biannual and annual checklists.  Once the hot water cylinder is hot, carry out temperature checks as per the monthly checklist.  Provided that all system components are working normally and the temperature measurements are satisfactory, the system may be put back into service immediately.  Ensure that the timer program is correctly set and switch the water heater back to timer operation by selecting: “run own program” on the control panel.

Correct use of Alpron system

Alpron is designed for use as a continuous decontamination system and is run through all dental instruments requiring water to operate.  Correct use of the system involves filling the bottled water system with RO water treated with Alpron concentrate diluted 10ml of Alpron to 990ml of RO water.  At the end of the day, the dental unit is drained down and any remaining bottled water is discarded and the bottle from the system stored inverted so that it dries.

Action in the event of a breakdown

In the event of a breakdown affecting the water system, the Responsible Person will decide what action is appropriate to restore proper service and what, if any, action is necessary pending repairs – for example, whether elements of the water system are to be taken out of service or whether clinical work must be suspended temporarily (refer also to the Business Continuity Plan).

Action in the event of an outbreak

In the event of an outbreak of legionella, the Statutory Duty Holder and the Responsible Person will meet to agree a plan of action.  This may include temporary closure of the practice, microbiological testing, disinfection of the water system, etc.  In the course of deciding their plan of action, the Statutory Duty Holder and Responsible Person may consult with appropriate bodies including the British Dental Association, an independent expert in the management of legionella risk (eg a member of the Legionella Control Association), Health and Safety Executive, local Primary Care Trust, Care Quality Commission, etc.  Detailed records will be kept of any action taken.

Legionella is not a notifiable disease in England but it may be necessary to inform the Health and Safety Executive to comply with RIDDOR if a member of staff is infected.

Water system schematic

To aid in the operation of this Written Scheme and the procedures set out in it, a detailed schematic of the practice water system has been prepared and a .pdf of this may be downloaded here.

Web version 5: 4.8.2016 (reviewed 1.9.2017)
Previous web versions published: 14.5.2011; 29.3.2012; 13.3.2013; 21.3.2013 (reviewed 20.6.2014; 5.6.2015)

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