9.6 Water quality issues beyond the point of supply

Under most jurisdictional legislation and arrangements within Australia, the responsibility of water suppliers ends at the point of supply to the customer, typically the water meter. The primary responsibility for ensuring that water supplied beyond the water meter remains safe and aesthetically acceptable rests with various stakeholders including:

• building and site owners or managers;

• plumbing and building regulators;

• plumbers;

• plumbing material suppliers;

• private individuals.

Under the catchment-to-consumer tap preventive management framework promoted by these Guidelines, however, water quality should be managed up to the point of consumption, usually the customer tap, to account for water quality changes that may arise as a result of the internal plumbing arrangements on customer properties. This management may be achieved by liaison between the water supplier and the stakeholders listed above.

Both microbial and chemical quality can deteriorate within buildings due to poor design and management of internal plumbing systems. While internal plumbing systems are largely outside of the control of water suppliers, incompatibility between the chemistry of drinking water as supplied and the quality and nature of internal plumbing and fittings can cause system-specific impacts, and it is reasonable to expect that water suppliers be aware of these issues. The two most common issues are:

• plumbosolvency – that is, mobilisation of lead into solution from lead pipes and brass fittings (which may contain traces of lead), and the solder used to join pipes, as a result of the supply of plumbosolvent water. The issue of plumbosolvency is rare in Australia. Similar issues can arise with the corrosion of pipes and fittings containing copper (cupprosolvency), leading to “blue” water;

• hardness – scaling of pipes, and of water elements in kettles and hot water services, resulting from the supply of very hard water.

Other possible impacts include the following:

• The supply of unbuffered desalinated water into areas not traditionally supplied with water of reduced salinity may exacerbate corrosion, particularly in hot water systems.

• Microbial and chemical contamination can be associated with distribution systems in large buildings. This risk arises particularly where large volumes of water are stored for extended periods in on-site header tanks, or ingress of untreated water occurs through faults in the pipe network, or there are cross-connections with non-drinking water supplies.

• Drinking water that sits unused in pipe networks for extended periods of time may have elevated levels of metals. This is seen particularly in schools after lengthy holiday breaks, where water to drinking fountains has remained stagnant in pipes, with the result that children have consumed water with elevated levels of copper (Scholz et al. 1995, Walker 1999, Brodlo et al. 2005).

Role of building and site owners and managers and plumbing oversight agencies

The Competition and Consumer Act 2010 requires plumbing and fittings to be fit for purpose, and that purpose includes being fit for the safe conveyance, storage and use of water of a chemistry as supplied within a particular area. Building and site owners, and managers and plumbing oversight agencies, are responsible for ensuring that the plumbing systems and fittings used within their areas of responsibility are fit to convey drinking water without leading to exceedances of water quality guidelines. In addition, these stakeholders should liaise with standards-setting bodies and water suppliers to ensure that the procedures for approving plumbing materials, fittings and systems are adequate, and that any products that are used comply with the requirements of AS/NZS 4020:2005: Testing of Products for Use in Contact with Drinking Water.

Role of water suppliers

Although Australian water suppliers are not responsible for the actions related to water quality management beyond the point of supply, they should be aware that the drinking water that they supply may interact with internal plumbing and cause unintended water quality issues (either aesthetic or health-related). The Competition and Consumer Act 2010 requires water supplied by water suppliers to be fit for purpose, including the conveyance, storage and use of that water within approved plumbing assets, fittings and plumbed-in systems available in water supply areas. In effect, this means that water suppliers have obligations if they are aware of potential negative impacts of mains water on correctly designed and installed plumbing systems.

Some recommended actions that water suppliers can take to minimise the risks associated with interaction of internal plumbing and supplied drinking water are:

• Liaise with relevant state-based plumbing authorities to ensure that plumbers use only materials that meet the requirements of AS/NZS 4020:2005: Testing of Products for Use in Contact with Drinking Water.

• Liaise with standards-setting bodies and plumbing regulators to ensure that the procedures for approving plumbing materials, fittings and systems are adequate to manage any short-, medium- and long-term risks associated with those materials, fittings and systems when carrying the water supplied in any particular supply area.

• Prepare information for customers on water quality issues that may have an adverse impact on their internal plumbing.

• Provide advice to customers with large reticulated networks on water quality issues that may arise from having stagnant water within their pipe networks.

• Develop and disseminate information to schools, highlighting, in particular, issues related to stagnant water, and suggesting that drinking fountains and other water-using devices be flushed before school returns after holiday periods.

• Ensure, wherever practicable, that each property is separately metered so that areas of low flow can be identified.

• In liaison with building and site owners and managers and plumbing oversight agencies, consider undertaking investigative monitoring studies to examine the interactions of water as supplied with the plumbing and fittings used in the water supply area.

Useful additional references on this issue include Rajaratnam et al. (2002), WHO and World Plumbing Council (2006), and WHO (2010).