9.6 Water quality issues beyond the point of supply (updated 2025)
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;
manufacturers and suppliers of plumbing materials and products;
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 the microbial and chemical quality of drinking water 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 (which can include water utilities, local councils or private water managers) and relevant health authorities and/or drinking water regulators, they should be aware of broader system-specific impacts such as:
incompatibility between the chemistry of drinking water as supplied and plumbing products;
in-premise water conditions including microbial water quality (see Section 5.5 on Opportunistic pathogens);
the quality and nature of internal plumbing and fittings.
The two most common issues are:
Leaching of metals – metals of concern can be released from plumbing products, in both dissolved and particulate form, via chemical and biochemical reactions and through physical abrasion of surfaces. This is particularly evident when there have been periods of stagnation where drinking water is sitting in contact with plumbing products for extended periods of time (e.g. days to weeks). This is seen particularly in schools after lengthy holiday breaks, where water to drinking fountains/bubblers has remained stagnant in pipes. For example, children returning to school after a break have consumed water with elevated levels of copper (Scholz et al. 1995; Walker 1999; Brodlo et al. 2005). Long periods of stagnation may also occur within sections of a building’s water distribution system, such as specific outlets that are not used frequently. Plumbing products that have deteriorated or corroded are more prone to releasing metals to drinking water (enHealth 2021).
Lead may be introduced into drinking water from plumbing products. Lead-based drinking water pipes are quite rare in Australia, having not been installed since the 1930s, while lead-based solder was phased out of use in Australia in the 1990s, with Australian Standards limiting lead in solders to less than 0.1% within drinking water distribution systems. However, historically brass plumbing products used in Australia were permitted to contain up to 4.5% lead (enHealth 2021), and while lead free plumbing products that typically contain no more than 0.25% lead are available, were not in common use. From 1 May 2026, only copper alloys containing no more than 0.25% lead are permitted for use in plumbing products in Australia (ABCB 2021, 2023).
a) Copper pipes are a common component of plumbing systems, and copper is also a major component of brass plumbing products, and as a result, copper may be present in drinking water. Elevated levels of copper in drinking water arising from corrosion of copper pipes used in plumbing systems can result in blue or green staining of plumbing fittings or basins.
b) Although reported less frequently, metals such as chromium, nickel, antimony and cadmium may also be present in drinking water due to their use in the manufacture of a variety of plumbing pipework and other products.
Elevated water hardness can cause scaling of both pipes and the water elements in kettles and hot water services. Such deposits can have indirect impacts on water safety including ingress of contamination due to reducing flow rates, increasing pressure and increasing the likelihood of the failure of backflow prevention measures.
Further information about risks from chemicals leaching from plumbing products, actions to reduce exposure and in-premise water sampling is provided in Information Sheet 4.1 (Metal and metalloid chemicals leaching from plumbing products).
Other possible impacts on water quality past the point of supply include the following:
The supply of very soft water or unbuffered desalinated water into areas not traditionally supplied with water of reduced softness or salinity may exacerbate corrosion, particularly in hot water systems.
Microbial and chemical contamination can be associated with distribution systems in large buildings. This risk increases where water is 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. See also Section 5.2 on Microorganisms in drinking water and Section 5.5. on Opportunistic pathogens.
Role of building and site owners and managers and plumbing oversight agencies
The Commonwealth Competition and Consumer Act 2010, and related state and territory legislation, requires plumbing and fittings to be fit for purpose, and that purpose includes being fit for the safe conveyance, storage and use of water, including its 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 products, fittings and systems are adequate, and that any products that are used comply with the requirements of the National Construction Code (NCC), Volume Three - Plumbing Code of Australia (PCA), developed and maintained by the Australian Building Codes Board (ABCB) (ABCB 2022). Building and site owners, and managers including residential strata body corporate managers and plumbing regulatory agencies, should ensure that building plumbing systems are constructed and managed in a manner that is fit for purpose, taking into consideration factors such as water quality, temperature and rates of water turnover (to prevent stagnation).
It is not unusual for new products (even if WaterMark certified) to initially leach chemicals into water in contact with them until such time as the products become conditioned, and a protective patina establishes on the inner surface of the fitting/fixture. A patina on metals and metallic alloys is a coating of various chemical compounds such as oxides, carbonates, sulfides, or sulfates formed on the wetted surface during exposure to water. This initial leaching reduces over time and virtually ceases once the patina is established. It is not well established how long the initial leaching period lasts, but it is widely accepted that this is largely affected by certain water parameters such as pH, hardness, corrosivity, alkalinity and temperature. Reducing potential exposure to the leaching of metals from plumbing products can be achieved at the tap by undertaking preventative flushing regimes as outlined in Information Sheet 4.1 (Metal and metalloid chemicals leaching from plumbing products).
To further minimise the risk of leaching, all plumbing works undertaken in Australia must be conducted by a licensed plumber, and licensed plumbers must use products that are WaterMark Certified in applications involving drinking water. The WaterMark Certification Scheme is administered by the ABCB and more information is available from local councils or plumbing regulators.
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, and related state and territory legislation, 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 products that meet the requirements of the Plumbing Code of Australia (ABCB 2022).
Liaise with standards-setting bodies and plumbing regulators to ensure that the procedures for approving and testing plumbing products, fittings and systems are adequate to manage any short-, medium- and long-term risks associated with those products, 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. This could be done in collaboration with relevant health authorities and/or drinking water regulators.
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 issues related to stagnant water within pipe systems, and suggesting that drinking fountains/bubblers 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 (2011).
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