Hazard, hazard source, and hazardous events
A hazard may be a biological or chemical agent or physical property of water that has the potential to cause injury or illness to an individual.
The following categories of hazard should be considered:
- biological hazards may include, but are not limited to, enteric pathogens (Escherichia coli (E. coli)), Campylobacter, Cryptosporidium, Giardia, and Enterovirus) and environmental pathogens (Legionella, Non-tuberculous mycobacteria (NTM), Pseudomonas aeruginosa).
- Chemical hazards may include, but are not limited to, metals (manganese, aluminium, copper, lead, nickel and cadmium) and trihalomethanes (THMs). THMs are a category of disinfection by-product formed by the reaction of chlorine with organic substances in water.
- Physical hazards may include, but not be limited to, high water temperatures, high or low pH and high levels of turbidity.
—many of the examples provided in the explanation of categories of hazard above will not be relevant to all facilities. Similarly, some facilities may identify hazards not listed in the examples provided above. The hazards a facility should include in their risk assessment should be based on factors such as, but not limited to, the age of the facility, nature of the water distribution system, history of illness, quality of incoming water, stored water etc. Facilities do not need to undertake monitoring for hazards that are not relevant to their water distribution system.
A hazard source is a location or condition that can give rise to a hazard. Hazard sources include, but are not limited to:
- areas of low flow or stagnant water within the facility distribution system (dead legs and disused taps)
- location of particular infrastructure (e.g. hot and cold water pipes too close together such that the hot water pipes raise the temperature of the cold water to temperatures favourable to Legionella growth)
- biofilm growth within pipework, storages and the plumbing fixtures
- incoming water to the facility which may contains hazards or contribute to the development of a hazard within the facility water distribution system
- poorly maintained or inadequate infrastructure including TMVs, tempering valves, backflow preventions devices.
A hazardous event is a situation that can lead to the presence of a hazard or increase its adverse impact. Hazardous events include, but are not limited to:
- interruption to supply - scheduled or unscheduled e.g. building/facility maintenance, natural disaster, road works, nearby construction or a water main break
- contamination of the incoming water leading to a boil water alert
- temperature changes in water (e.g. a decrease in temperature in a hot water system to below 60°C provides conditions conducive to Legionella growth).
A more detailed description of potential hazards and hazardous events for facility water distribution systems can be found in the description of hazards and hazardous events.
These are the key steps that your facility should cover:
- List all possible types of hazards, hazard sources, within your water supply system and hazardous events likely to affect your facility (consider differing affects associated with staff, public, residents or patients’ high risk to low risk).
- Review the list of identified hazard sources within your water supply system and implement corrective actions and preventative control measures to eliminate or minimise the associated risk (e.g. ensure all hot water plant and temperature control devices are correctly maintained and operating at their optimum, implement a weekly flushing regime to all low flow and infrequently used outlets)
- Implement operational and verification monitoring of your control measures to ensure your risk control measures are effective.
- Ensure detailed records of the control measures and monitoring are kept for review (e.g. equipment registers and maintenance records for temperature control device, backflow valves, hot water plant, etc).
- An estimation of the duration of an incident and the capacity of your facility to “endure” an incident can also be useful (for example, interruption to the water supply to the facility).
- Your water distribution system description (including flow diagram and inventory list) should be used to assist you with this task.
Examples of hazards and hazardous events, listed by source/system component
|Hazard Source/System Component||Hazards||Hazardous events|
Boundary to building plumbing
Cold water storage
Cold water distribution
Central hot water system
Warm water loops
Drinking water fountains
- National enHealth guidelines for Legionella control (PDF, 577KB) - section 2.2 (page 10)
- National risk management plan template (DOC, 164KB) - section 2.2 (page 6 to 7)