Downstream supply
Information for suppliers who receive drinking water from one supply and then distribute it to consumers via a different supply.
On this page you'll find key information about how to provide safe drinking water to your community and meet your legal obligations under the Water Services Act 2021.
Note: the rules for downstream supplies come into effect on 1 July 2027. Further guidance will be added to this page before then.
Are you a downstream supplier?
Downstream suppliers receive water (either treated, untreated or partially treated) from one supply (the ‘upstream supply’) then distribute it to consumers using a different supply (the ‘downstream supply’).
The Authority's policy statement categorises a supply as downstream only if:
- the upstream and downstream supplies are owned by different people or organisations, and
- the downstream supply either:
- includes treatment steps to make the water safe to drink (e.g. primary disinfection, residual disinfection, coagulation, sedimentation, filtration) or to address other issues (e.g. potassium permanganate to improve the appearance of the water)
or
-
- includes no treatment and is at risk of microbiological and/or chemical contamination that might make the water unsafe to drink (see Understanding risks from microbiological and chemical contaminants below).
If you don’t meet these criteria, you might still have responsibilities under the Water Services Act 2021outbound.
Find out what type of drinking water supply you provide and the requirements that apply to you.
Examples of downstream supplies
- A rural town receives untreated water from a nearby mixed-use rural water supply. The town has a treatment plant and is therefore classified as a downstream supply. The mixed-use rural supply is the upstream supply.
- An industrial site receives treated water from a nearby town. The site has booster chlorination and fluoridation facilities installed. The site is therefore a downstream supply and the town supply is the upstream supply.
- A town receives treated water from a nearby campus. The town’s network includes fire hydrants. The campus is the upstream supply and must follow source, treatment and distribution rules. The town is classified as a downstream supply because of its risks to the distribution network.
Example that is not a downstream supply
- A private connection to a city water supply serves approximately 10 houses. Source, treatment and distribution rules apply to the city supply. The private network has no treatment, fire hydrants or other distribution risk factors so it is not classified as a downstream supply.
Understanding risks from microbiological or chemical contaminants
As explained in the examples above, even if the water provided to you by an upstream supply is treated and the upstream supply is fully compliant with the requirements of the Act, your downstream supply could allow microbiological or chemical contaminants into the water.
There are specific risk factors:
- Scour valves, network pumps or pump stations, fire hydrants or pressure-reducing valves included in the downstream supply can create conditions that increase the risk of contamination.
- Extensive storage of water in tanks within your downstream network (not small storage tanks serving individual properties) increases the risk of exposing the water to external contaminants. Extensive storage means a volume of water equivalent to 24 or more hours of supply for the entire network during times of low demand.
- External connections to your downstream supply (e.g. stock troughs, swimming pools, industrial sites) that are not protected against backflow can allow potentially contaminated water to flow backwards into the drinking water supply.
Most downstream supplies will face one or more of these risks, even if the upstream supply is treated and fully compliant with the Act. These risks need to be managed to ensure your community receives water that’s safe to drink.
The health risks are real
Germs (bacteria, viruses, protozoa) can get into the water and make people who drink it sick. Children, the elderly and people who are already unwell are most at risk.
Chemicals (e.g. lead) can be introduced when the water is treated and distributed. Elevated levels of chemicals can be a health risk.
Your responsibilities as a drinking water supplier
In Aotearoa New Zealand, drinking water is regulated through different Acts, rules and requirements. These exist to make sure everyone can access safe drinking water.
As a downstream supplier, you will have legal responsibilities under the Water Services Act 2021outbound to ensure your community receives safe drinking water. Your options for meeting these responsibilities will vary depending on:
- whether the water you receive from the upstream supply is treated, untreated or partially treated
- the specific contamination risks faced by your downstream supply
- the treatment steps (if any) included in your downstream supply
- the characteristics of your downstream supply (e.g. if it serves multiple properties, or buildings on only one property)
- the number of people who normally use the water.
The following sections direct you to guidance on what you will need to do from 1 July 2027 to meet your legal responsibilities, depending on the variables above.
Note: downstream supplies are currently referred to as linked supplies in Hinekōrakooutbound – our self-service portal for drinking water suppliers. We are currently working to update this.
Requirements if you receive treated water from an upstream supply
There are legal requirements for downstream suppliers who receive treated water from an upstream supply.
These requirements are to ensure your community receives safe and sufficient drinking water. The requirements manage the risks described under Understanding risks from microbiological and chemical contaminants above and can be met by following the relevant Drinking Water Quality Assurance Rules or, in some cases, Acceptable Solution.
The rules that will apply to you depend on how many people normally use your water. In each instance, only the general and distribution rules will apply because you are receiving treated water from an upstream supply. The source water and treatment rules are the responsibility of the upstream supplier.
For supplies that normally serve 25 or fewer people ONLY for domestic purposes
You don’t have any specific legal requirements under the Act. However, learn about the steps you can take to ensure your community receives safe drinking water.
For supplies that normally serve 25 or fewer people for public or commercial purposes (e.g. café, sports club, marae)
Follow the rules for a Very Small Community Supply.
For supplies that normally serve between 26 and 100 people
Follow the general and distribution rules for a Small Networked Supply.
For supplies that normally serve between 101 and 500 people
Follow the general and distribution rules for a Medium Networked Supply
For supplies that normally serve more than 500 people
Follow the general and distribution rules for a Large Networked Supply.
Requirements if you receive untreated or partially treated water from an upstream supply
There are legal requirements for downstream suppliers who receive untreated or partially treated water from an upstream supply and then distribute it to either:
- consumers on multiple properties via a network of pipes (which may or may not include tanks for extensive storage)
- consumers in up to 10 buildings on the same property or adjacent properties with common ownership.
These requirements are to ensure your community receives safe and sufficient drinking water. The requirements manage the risks described under Understanding risks from microbiological and chemical contaminants above and can be met by following the relevant Drinking Water Quality Assurance Rules or, in some cases, by following an Acceptable Solution.
The rules that will apply to you depend on the characteristics of your supply and the number of people it serves. In either case, the source water rules do not apply. They are the responsibility of the upstream supplier.
Consumers on multiple properties
For supplies that normally serve 25 or fewer people ONLY for domestic purposes
You don’t have any specific legal requirements. However, learn about the steps you can take to ensure your community receives safe drinking water.
For supplies that normally serve 25 or fewer people for public or commercial or purposes (e.g. café, sports club, marae)
Follow the rules for a Very Small Community Supply.
For supplies that normally serve between 26 and 100 people
Follow the general, treatment and distribution rules or the Acceptable Solution for a Small Networked Supply.
For supplies that normally serve between 101 and 500 people
Follow the general, treatment and distribution rules or the Acceptable Solution for a Medium Networked Supply.
For supplies that normally serve more than 500 people
Follow the general, treatment and distribution rules for a Large Networked Supply.
For supplies that serve a consumer population of any size, where at least 50 percent of the water is used for agricultural or horticultural purposes and the rest for domestic purposes
You can meet your legal requirements by following the Mixed-use Rural Acceptable Solution.
Consumers in up to 10 buildings on one property or adjacent properties with common ownership
For supplies that normally serve 25 or fewer people and ONLY for domestic purposes
You don’t have any specific legal requirements. However, learn about the steps you can take to ensure your community receives safe drinking water.
For supplies that normally serve 25 or fewer people for public or commercial purposes (e.g. café, sports club, marae)
Follow the rules for a Very Small Community Supply.
For supplies that normally serve between 26 and 100 people
Follow the general and treatment rules or the Acceptable Solution for a Small Self-supplied Buildings Supply.
For supplies that normally serve between 101 and 500 people
Follow the general and treatment rules or the Acceptable Solution for a Medium Self-supplied Buildings Supply.
For supplies that normally serve more than 500 people
Follow the general and treatment rules for a Large Self-supplied Buildings Supply.
Exemptions
Our regulatory system has been designed for most drinking water suppliers. For some drinking water suppliers, it might be unreasonable or impractical to comply with certain requirements in the Act. These suppliers can apply for an exemption from one or more of these requirements.
Head to the exemptions page for information on types of exemptions and how to apply.
This webpage is intended as a guideline and summarises legal requirements but does not address every requirement under the Water Services Act. It is not intended to be definitive and is not legal advice. Drinking water suppliers are responsible for understanding and complying with their legislative duties. The Authority may review and revise this page over time. If you are using a printed copy, please check the website to make sure it is up to date.