Drinking Water for New Zealand

Managed by ESR for the Ministry of Health.         Data extracted from the National DWO Database.

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Frequently Asked Questions on managing New Zealand drinking-water

Use this page as a quick starter. Note that in order to keep answers brief but accurate in the typical situation, they may be ignoring complexity and the special handling used in a minority of cases.

The Questions

What is E. coli and why is it measured?

A danger wih any water supply is that human or animal excrement can somehow contaminate the water, passing on illness-causing micro-organisms (pathogens) to those who later drink it.

Analysis of water for all possible pathogens would be prohibitively expensive, so some sort of "indicator' test is required - a test for something that will give an indication of how microbiologically safe the water is for drinking. E. coli is that indicator.

E. coli, or Escherichia coli, to use its full name, is a common gut bacteria living in humans and warm-blooded animals and excreted by them.

While it doesn't usually cause illness on its own (there are some serious exceptions), its presence in drinking-water is used to indicate that the water has been subjected to recent faecal contamination. Therefore if E. coli is present, there is a greater risk of pathogens also being there.

What is FAC?

FAC is 'Free Available Chlorine", and refers to residual chlorine remaining in water after it has been chlorinated. Treatment plant operators can measure the FAC, either on a single sample or continuously using a probe.

This FAC is "Available" to provide a certain amount of disinfection should bacteria be present anywhere in the reticulation. Its continuous presence, above a certain minimum level, indicates that water leaving the treatment plant has been adequately treated for bacteria.

What are Giardia and Cryptosporidium?    Go to top

These are protozoa, single-celled micro-organisms that are somewhat larger than bacteria and have a tough outer coat. They live and multiply in the intestine, causing fever, diarrhea, abdominal cramps and vomiting, which can last for many days. In some people, especially those with weakened immune systems, the illness can be life-threatening.

In water sources they may exist for long periods as cysts, multiplying only after re-entering the intestine of a human or warm-blooded animal.

Unlike E. coli and other bacteria, protozoa are very resistant to chlorination. Therefore treament focuses on very fine filtration to remove them, disinfection with ozone or chlorine dioxide, or the use of deep groundwater that is known to be secure from surface contamination.

Which Government Department has oversight of community drinking-water quality?

The Ministry of Health, through the provision of standards, guidelines and other tools, ensures that an appropriate infrastructure is present in New Zealand to support the provision of clean and safe drinking-watter to communities. Links to Ministry documents

Who is responsible for monitoring water quality and ensuring a supply complies with the Drinking-water Standards?

The water supply owner. For larger supplies this is usually the city or district council. For private supplies it is the owner. For schools on their own supply, it is the school board of trustees. More

What is the Public Health Grading?    Go to top

A statement of the extent to which a supply achieves and can ensure a consistently safe and wholesome product. It is expressed by a combination of grading letters, for example: A1a1 is best, Aa or Bb is good, Cc is marginal, Dd is unsatisfactory and Ee is unacceptable (many other combinations are of course possible, eg Ab, Cb etc.), The upper-case part refers to the grade as it leaves the treatment plant, while the lower case refers to the water at the consumers' gate. More about grading

What is the Annual Review?

The Annual Review is a major report prepared for the Ministry of Health identifying which supplies complied with the drinking-water standards for a particular year, and the reasons for non-compliance for the others.

Drinking-Water Assessors (DWAs) of District Health Boards gather and audit monitoring and compliance data from water suppliers, then forward it to ESR for analysis and reporting to MoH. The final report is released to the public by MoH about 12 months after the report period ends.

From 2006 onwards, the Annual Review period was changed from a calendar year to a 12 month period starting each year on 1 July.

What is a community drinking-water supply? 

Any drinking-water supply serving 25 or more people for at least 60 days a year. this includes many schools, permanent camp sites and marae. more

What is the 'Register of Drinking-Water Suppliers in New Zealand'?

An annual document released by the Ministry of Health which lists information about community supplies in New Zealand, including their structure and grading. With over 2,000 supplies, the A4 printed version is over 400 pages long.

You can download a pdf copy of this document from the Ministry website (choose a link) or, if you want to see exactly the same information for a particular supply, choose it from the water supplies pages on this website. for example, the Register entry for Timaru looks like this.

NOTE: Printing of the Register was discontinued in 2007. Use this website to see supply details.

What are zones, plants and sources?

Zones (or Distribution Zones) are that part of the town or community receiving water of similar quality. For a small supply, that means "everywhere". For larger supplies, it may be only part of a town or city. By definition, parts receiving different water will be in different zones.

Plant means the treatment plant supplying the water. In some situations where no treatment is given, a nominal plant is defined as where the water is pumped from or merely gathered together. In others, the treatment plant will have highly technical operations with extensive automated control and monitoring of water quality.

Source is the river, groundwater, or other source from which the water is taken. About half of New Zealandís drinking-water is pumped from the ground, with the remainder coming from surface sources. Many larger supplies will have several sources. more

Must a supply comply with the Drinking-water Standards?

While it is strongly in the best interests of the community to have water that is demonstrably safe to drink, there are a range of dates by which time water suppliers must comply with the requirements of the Health (Drinking Water) Amendment Act 2007.

There are five main population bands specified. The largest supplies must comply by 1 July 2009, the smallest by 1 July 2013 and the others for years in-between.

Failing to meet the standards in a particular year will not be a requirement in itself, provided the supplier can demonstrate that they have taken 'all practicable steps' in an attempt to do so.

Note that these are broad summary statements. Read the Act here or as a pdf for the full authoritative details.

Who is responsible for this website?    Go to top

This site is run by the ESR Water Information Systems team, a mix of scientists and information systems people based in Christchurch, New Zealand. This website, along with development and management of the WINZ (Water Information for New Zealand) database and associated water quality areas, is performed under contract for the Ministry of Health.

ESR, or the "Institute of Environmental Science and Research Limited", is a Crown Research Institute with major sites in Auckland, Wellington and Christchurch.

To quote from the ESR website, "ESR's mission is to protect people and their environment through science. We are New Zealand's leading provider of scientific services in environmental health and forensic science. We deliver consulting, analytical and research services to meet the needs of government, industry and the public."



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