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Verification monitoring

Verification monitoring confirms whether your water risk management plan (WRMP) is effectively managing the risks associated with water quality within your water distribution system.

Verification monitoring consists of collecting water samples from selected locations within your water distribution system and testing for the hazards that are being controlled. This clearly includes Legionella bacteria, but if the control measures included in the WRMP are also intended to remove or prevent colonisation by other pathogens like Pseudomonas or non-tuberculous mycobacteria, then these pathogens could be included in the verification monitoring.

It is not recommended to include heterotrophic colony count (HCC), or heterotrophic plate count (HPC) in a verification monitoring program as heterotrophic bacteria are not hazards in themselves. However, monitoring the changes in HCC between water entering a facility and reaching more distal points can be used to indicate parts of the water distribution system where stagnation may be occurring, leading to microbial growth.

In hospitals and aged care there may be physical and chemical hazards that must be monitored as well as microbial ones.

Verification monitoring does not generally occur in real-time or as frequently as operational monitoring but may be done at the same monitoring location.

When collecting water samples for verification of the inactivation of microbial hazards, parameters usually included in operational monitoring (such as free chlorine residual and temperature) should also be recorded to assist in the interpretation of any detections of these microbial hazards.


Verification monitoring tests are conducted at an analytical laboratory accredited for the analytical test method used to ensure the highest level of accuracy.  

Test methods used and time taken to obtain a result vary for different parameters. For example the AS/NZS 3896 and ISO 11731 culture methods for Legionella testing take up to 10 days before a result is known.

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Details of the verification monitoring program (locations, frequency, parameters) should be documented in your WRMP.

If verification monitoring results show that control measures are not effectively controlling the hazard, an appropriate corrective action which brings the hazard back under control should be put in place. This may also require changes to the control measure.

These are the key steps that your facility should consider:

  • Select the parameters to be tested for during verification monitoring.
  • Determine the frequency to test for each selected parameter – the verification monitoring frequency should be based on the outcomes of the facility’s water risk assessment.
  • Determine the location(s) to test for each selected parameter – the verification monitoring location(s) should be based on the outcomes of the facility’s water risk assessment.
  • If verification monitoring detects the targeted microbial hazards, at any concentration, this suggests that the control measures in place under the WRMP are not effectively controlling the hazard. In this case, the control measures will have to be reassessed and made more effective or additional measures will have to be introduced into the plan.
  • Ensure records are kept for each monitoring activity and any corrective action implemented as part of the response to the detection.


Last updated: 24 January 2017