The purpose of a control measure is to prevent or reduce the level of risk associated with a hazard or hazardous event to an acceptable level. This could be through activities such as regular maintenance, corrective actions or performing an operational response.
Under section 61D(d) of the Public Health Act 2005, a water risk management plan (WRMP) must state the control measures to be implemented for the risks identified in the risk assessment. It must also include a record of how results, obtained from procedures and schedules set up to implement the control measures, will be kept.
When to implement a control measure
The risk assessment should identify a level of risk for each hazard and hazardous event identified in the WRMP.
Based on a pre‑determined level of risk that each facility is willing to accept (without the implementation of additional control measures), the level of risk for each hazard and hazardous event, as determined by the risk assessment, will present either an “acceptable” or “unacceptable” level of risk.
Control measures should be implemented for risks identified as unacceptable to either prevent an occurrence or to reduce the level of risk to an acceptable level.
If the level of risk is found to still be unacceptable after implementing a control measure, additional control measures should be implemented to reduce the level of risk to an acceptable level.
What to consider when implementing a control measure
Factors to consider when determining whether to apply a control measure at a particular point in your water distribution systems:
- presence of an existing control measure for the identified hazard or hazardous event at this point
- effectiveness of the control measure at this point (e.g. will it remove or minimise the hazard)
- can the control measure be monitored easily to verify its effectiveness
- potential for introducing new hazards at this point (e.g. introducing chemical disinfection may reduce microbial risk but introduce a chemical hazard from potential overdosing)
- safety of employing the control measure at this point (e.g. are facility staff properly trained in handling concentrated disinfectant solutions like sodium hypochlorite)
- alternative point at which the hazard levels can be controlled.
Written requirements for control measures
All control measures must have a written procedure, including a frequency schedule (for maintenance and monitoring), detailing how to implement the control measure.
All control measures, irrespective of the level of risk (acceptable or unacceptable, as determined by the risk assessment) should be recorded in the risk assessment table of your WRMP.
Key control measures
The particular set of control measures implemented as part of facility water risk management plans will depend on the hazards and hazardous events identified in the plan. Some of the more important potential control measures are shown below, but many other measures are possible.
The ability of existing staff to identify problems with the water distribution system should not be underestimated. Staff may quickly notice that water is not heating properly, or is discoloured, before it can be picked up by routine monitoring.
The WRMP should identify the types of observations that should be reported and the procedures for reporting them. All staff should be trained in these procedures.
The water risk management team must ensure the WRMP includes measures to ensure that hot water systems operate in the most effective manner for control of Legionella and other identified hazards.
Some control measures are required by regulation. For example, the Plumbing Code of Australia requires that hot water systems heat water to above 60°C, but do not exceed 50°C at hot water outlets in domestic situations. For hospitals, aged care facilities and child care centres, water should not be exceed 45°C at the outlet where patients or residents may be exposed. These measures are designed to help reduce Legionella, while also preventing scalds.
The balance between the requirements for Legionella control and scald prevention requires careful management by health, aged and child care facilities.
Where possible, cold water systems should be maintained below 20°C to prevent biofilm and Legionella growth.
There is no requirement for the water supplied by the drinking water service provider to be below the temperature for Legionella control (20°C). For much of the year ambient temperatures in Queensland are such that the incoming water from drinking water service providers is frequently above 20°C, particularly if the water is supplied from a bore water source.
Measures to limit unnecessary heating of water include:
- locating cold water storage tanks in shaded areas or installing shade
- not locating cold water pipes in uninsulated roof cavities
- not locating cold water pipes in close proximity to hot water pipes, and when this cannot be avoided, ensure that both hot and cold water pipes are appropriately lagged.
In Queensland, drinking water supplied by registered drinking water service providers should not contain detectable E. coli, which is an indicator of faecal contamination of water. However, this does not mean the water will have sufficient disinfection residual to prevent biofilm growth or kill other pathogens after it reaches your facility.
If your risk assessment finds that the disinfection residual of the incoming water is too low, it should in the first instance be discussed with your drinking water service provider. It may be that they are able to take actions that will ensure you receive water with a suitable disinfectant residual concentration. If this is not possible, you may need to increase alternative control measures such as filtration of incoming water or more frequent or prolonged flushing to get fresher water through your facility that might have a higher disinfectant residual. In some circumstances, it may be necessary to discuss alternative disinfection options with a suitably qualified plumber or consultant. If in doubt, contact your local Queensland Health public health unit for advice.
Your facility should only consider installing chemical disinfection as a last resort. On-site disinfection introduces a new set of hazards that need to be assessed and managed and requires specialist skills and considerable time. You should not consider installing on-site disinfection unless all other options have been tried and microbiological contamination persists.
An option is to be ‘disinfection ready’. This enables your water system to be chemically disinfected in a one-off procedure should Legionella or other microorganisms not be controlled by other methods. To be ‘disinfection ready’ you can have your plumber install a chlorine dosing point at a suitable place in your system during the next scheduled maintenance visit. Providing there is a suitable, safe and accessible point available, this should not be expensive.
Routine maintenance of all relevant plumbing fixtures is an important control measure. Ensuring that thermostatic mixing valves (TMVs), backflow prevention devices, ice machines, hot water services, filters and other equipment undergo regular maintenance as required by the Plumbing Code of Australia, or by the manufacturer’s recommendations, is an important function of the WRMP.
If your plan has identified more significant problems, such as dead legs, non-return legs, or inappropriate fittings, consider a program to manage or replace these over time as part of the routine maintenance schedule.
Responses to potential loss of supply
In view of the frequency of natural disasters in Queensland, all healthcare water risk management plans must have considered their capacity to respond to:
- a total loss of drinking water supply, considering various periods from a few hours to several days
- any of a number of different contamination scenarios, including “dirty water” (i.e. discoloured water of unknown cause) or other microbial or chemical contamination. These may be notified to you by your drinking water service provider via a “boil water alert” or “do not drink alert”.
- National enHealth guidelines for Legionella control (PDF, 577KB) - section 3.1 (pages 17 to 25)
- National risk management plan template (DOC, 164KB) - section 3.1 (page 10)