Updated source water classes for large drinking water suppliers
Find out how source water classifications will change following amendments to the Drinking Water Quality Assurance Rules for large suppliers.
Changes to the level 3 Drinking Water Quality Assurance Rules, announced in June 2026 and coming into effect in July 2027, aim to make it easier for drinking water suppliers who provide water to a base population of more than 500 people to comply with legislative requirements.
A key change is the simplification and clarification of source water classifications, including the introduction of a new Class A category.
View the updated Drinking Water Quality Assurance Rules
View the current Drinking Water Quality Assurance Rules (these rules will be replaced by the updated rules from 1 July 2027).
New source water classes
By default, current classifications for large drinking water suppliers will change as follows:
|
Current class |
Default New Class |
|
N/A |
Class A |
|
Class 1 |
Class B |
|
Class 2 |
Class C |
|
Class 3 |
Class D |
|
Class 4 |
Class C |
If a supplier elects to stay with their new default class, they do not need to reassess their water supply and can expect few changes in their day-to-day operations and monitoring responsibilities.
However, all suppliers will have the option to:
- drop down to a lower class without having to reassess their water supply
- move to a higher class, which will require an assessment of their source water.
All classes can be found in section 8 of the updated Drinking Water Quality Assurance Rules.
New Class A water sources
The Authority has established a new Class A category for certain groundwater sources that have a documented unbroken three-year history of no biological MAV exceedances in test results. This category will be available to use from 1 July 2027 as updated rules come into effect.
Under the updated rules, no treatment barriers will be required for water sources that meet Class A criteria. However, residual disinfection is still required.
If a water supplier wishes to become a Class A supplier but does not have the qualifying testing history, they can apply to become a Class A (interim) water source. They can then either demonstrate that they meet Class A requirements (see below) or join another class following an assessment.
Class A requirements
To meet the Class A requirements, source water must be groundwater abstracted from a depth of greater than 30 metres below the ground via a sanitary bore head.
Suppliers must also be able to demonstrate that their source water is safe from biological contamination. Suppliers choosing this pathway have one of two options to classify a source as Class A:
|
Evidence of Testing Option |
Interim Option |
|
|
|
If E. coli, total coliforms or F-specific RNA bacteriophage are detected, or the integrity of the groundwater is compromised in other ways, an assessment must be done as soon as possible.
This assessment must:
- determine the likely cause of the contamination
- identify any actions that need to be taken to protect public health
- include investigative sampling involving:
- daily monitoring for E. coli and total coliforms for 36 consecutive days, followed by weekly monitoring for a further 47 weeks (to make up a total monitoring period of 52 weeks); and
- weekly testing for F-specific RNA bacteriophage for two months, followed by monthly testing for another two months and four samples evenly spaced over the next eight months.
- determine whether the source water still meets the criteria for Class A or if reassessment is required to determine an appropriate class.
Class A (interim) requirements
Class A (interim) is for drinking water suppliers who intend to meet the criteria for Class A but do not yet have the required monitoring data. Class A (interim) is a temporary class, and gives the supplier 24 months to either meet the requirements of Class A or drop down into Class B or Class C.
For a water source to move from Class A (interim) to Class A, a Class A (interim) supplier must demonstrate that their water source is safe from biological contamination. The supplier can choose one of two options to demonstrate this for monitoring E. coli and total coliforms. The monitoring requirement for F-specific RNA bacteriophage is the same for both options.
|
Option 1 |
Option 2 |
|
No E. coli and/or total coliforms detected in drinking water samples taken over a period of at least three uninterrupted years (with at least 12 samples taken at evenly spaced intervals per year) |
No E. coli and/or total coliforms detected in drinking water samples after daily monitoring for 36 consecutive days, followed by weekly monitoring for a further 47 weeks (to make up a total monitoring period of 52 weeks) |
|
No F-specific RNA bacteriophage detected in drinking water samples after consecutive weekly monitoring for two months, followed by monthly monitoring for another two months and four samples evenly spaced over the remaining eight months. |
|
If E. coli and/or total coliforms or F-specific RNA bacteriophage are detected, or the integrity of the groundwater is compromised in other ways, an assessment must be done as soon as possible.
This assessment must:
- determine the likely cause of the contamination
- identify any actions that need to be taken to protect public health.
If there is enough time remaining in the 24-month qualification period to complete a new year-long testing program for E. coli, total coliforms and F-specific RNA bacteriophage, water suppliers can continue to try to establish a Class A water source.
If there is not enough time, the water source must instead be classified as either Class B or Class C.
This webpage is intended as a guideline and summarises legal requirements but does not address every requirement under the Water Services Act and the Drinking Water Quality Assurance Rules. 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.