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Remedial flushing for a Legionella detection

Remedial flushing, after a confirmed Legionella detection, minimises the potential for exposure of the occupants by the immediate removal of contaminated water through either the entire facility or a localised area of the water distribution system.  

When to undertake remedial flushing

When Legionella is detected within your water distribution system, flushing is one of several options available to reduce the immediate exposure to patients/residents and should be performed in conjunction with procedures for checking disinfection residual and temperature.

Flushing should be performed in accordance with your facility’s water risk management plan (WRMP) and in consultation with your water risk management team.

There are other options available such as, but not limited to, thermal treatment (pasteurisation), superchlorination (hyperchlorination), introduction of routine chlorine dosing and a chemical clean. These options require specialised professionals to perform e.g. licensed plumbers or approved contractors.

Where to undertake remedial flushing

Flushing should be based on the location and source (tap/shower) of the Legionella detection, which may affect an entire facility or only a limited number of outlet(s) in a localised area (e.g. single wing, ward or cluster of rooms).

The risk of exposure to vulnerable patients/residents should be controlled as a priority. This may include isolation of the affected room(s), relocation of patients/residents (if the risk of moving them is less than the risk of legionellosis) or isolation of the affected water supply.

Who should undertake remedial flushing

The flushing procedure should be performed by trained and competent staff.

A workplace health and safety officer should be consulted before carrying out any flushing as personal protective equipment (PPE) may be required (scald protection, microbial protection).

Steps

When Legionella is detected, main steps for flushing should meet the following criteria:

  • In the affected area, tapware aerators and flow restrictors (if fitted) should be removed to ensure there is enough flow through taps. These fittings should be physically and if necessary chemically cleaned (to remove rust and lime scale deposits) and disinfected before reinstallation.
  • In the affected area, shower heads should be removed (if possible), cleaned and then disinfected. This may not be practical for fixed shower heads, but is advisable for flexible hoses. Where a point of use filter is installed as part of the shower head, this should be removed before flushing commences. Replacement of a point of use filter will depend on the nature of the contamination event.
  • In the affected area, turn on the cold water taps and flush for at least 5 minutes.
  • In the affected area, turn on the hot taps and flush for at least 5 minutes (longer flushing may be required in large facilities with complex systems).
  • The time period for effective flushing can be checked by measuring the disinfection residual at the outlet.
  • In the affected area, flush plumbed-in appliances according to manufacturer’s guidelines, including, but not limited to: ice makers, chilled water dispensers and replace potentially affected water filters.
  • In the affected area, flush and clean all other devices that may have used the contaminated water such as, but not limited to: Continuous Positive Airway Pressure (CPAP) devices, humidifiers, coffee makers and water jug filters.

Caution

  • During decontamination of a facility water distribution system all efforts should be made to protect vulnerable patients/residents by minimising their exposure to contaminated aerosols. An assessment of the likelihood of exposure should be made with reference to the extent of contamination indicated by the Legionella/microbial test results.
  • Stringent control measures must be implemented to prevent the risk of scalding.
  • Outlet(s) should be covered with a damp towel during the flushing procedure to minimise generation of aerosols. Alternately, a hose connected to the outlet(s) should direct the water into the fixture waste and any exhaust fans should be turned on.
  • If rooms have forced ventilation (ceiling extractor fans) these should be turned on before flushing and left operating for at least 1 minute after flushing has been completed.
  • In bathrooms, the door should be left slightly ajar to allow clean air to enter the room and replace any aerosols generated during the process.
  • Ensure no outlets are missed. Outlets in vacant rooms or storage areas can easily be overlooked and become reservoirs for contamination of the rest of the system.

After flushing procedure

Routine flushing frequency should increase until resamples have been collected and tested for Legionella to demonstrate outlets have been successfully decontaminated. Resamples should not be collected less than 3 days or after 7 days from treatment.

Detailed documentation should be kept to provide evidence of flushing of all affected outlets, surrounding outlets or the entire water distribution system, as applicable.

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Last updated: 23 January 2017