How safe is your drinking-water? Warning - this report may leave an unpleasant taste in your mouth!

• In 2005 102,000 people were served by registered supplies with water containing unacceptable levels of E. coli.
• 84,000 were exposed to greater risk of disease as the supplier did not take immediate steps to correct the problem once E. coli was found.
• In 111 schools the water supply was contaminated with E. coli during 2005.

These are just three of the findings of the Ministry of Health's Annual Review of the Microbiological and Chemical Quality of Drinking Water in New Zealand. The document covers the 2005 year and was published on 30 January 2007.

The review measures water quality against the Drinking Water Standards for New Zealand: 2000.

The standards give top priority to microbiological quality because bacteria and protozoa can cause rapid and major outbreaks of illness. The bacterium Escherichia coli (E. coli) is used as an indicator that the water has been contaminated by human, bird or animal faeces and water providers are required to check for its presence.

The protozoan cryptosporidium is also used as a measure of a water's safety but it's difficult to check for its presence as it is not evenly distributed through water. Providers must have systems in place to monitor water quality and to remove these contaminants from the water supply.

Approximately 76 percent of New Zealanders received water that has been shown to meet the requirements for protection against E. coli, and 71 percent received water that met the requirements for cryptosporidium. Most large communities - towns with more than 5,000 people - had water supplies which met these requirements, but many smaller communities were supplied with water which was not microbiologically safe.

Unsafe water

Twenty four percent (980,000) of New Zealanders are supplied with water that isn't known to be safe to drink.

Of those, nearly half, (460,000) get their drinking-water from rooftop tanks or bores. Their supplies aren't included in the Review, but a recent Massey University study found that more than half of 560 samples from private rooftop supplies were contaminated by faecal matter.

Two percent - 102,000 - received water that had been contaminated by E. coli. Most lived in small communities but serious failures occurred. In Blenheim and North End Oamaru too many samples were contaminated with E. coli, and in Kawerau and Matamata the suppliers failed to take appropriate action once E. coli was found.

Most of the rest had water that didn't comply with the standard because it was not checked often enough to show that it was safe from E. coli.

It's a concern that 145 small supplies - including schools, motor camps, maraes, hotels and lodges - stopped monitoring their water quality in 2005. Forty-one of them had been found to have E. coli in their water during 2004. Some were maraes and schools and schools serving very small numbers, but among them were hotels and camps - Tolaga Bay Motor Camp, Punakaiki Rocks Hotel, Purau Motor Camp - where visitors might not be aware of the risks in drinking the water.

Water in schools

Many schools have inadequate treatment or monitoring. There are 624 schools with their own water supply, but only 81 provided adequate protection against E. coli.

Children are especially vulnerable to infections so it is important they have access to safe water. Boards of Trustees are responsible for testing water supplies and for minor upgrades, ongoing maintenance and operating costs. Where a major upgrade is necessary, the Ministry of Education will carry out the work under its capital costs programme.

Hospitals and health service providers

Hospital patients are another group at high risk of water-borne infections. Of the nine healthcare providers with their own water supply, Princess Margaret Hospital in Christchurch and Ashburton Hospital had inadequate monitoring and the Waiheke Health Trust supply was found to contain E. coli.

We say

It's encouraging that the proportion of New Zealanders supplied with safe drinking-water continues to increase - up two percent from 2004. But in 2005 there was an increase in the number of people in supplies that were not monitored, and a large increase in those with supplies where appropriate action wasn't taken after E. coli was found.

Unless it's taken from an enclosed aquifer, such as the one which supplies Christchurch, New Zealand groundwater can be assumed to be contaminated by faecal matter. Drinking-water suppliers should treat and monitor their water to make sure it is safe, or warn consumers of the risks.

More help

To find out more about the quality of your water supply contact your supplier (your local council can tell you how), or the public health unit of your District Health Board.

Annual review of Drinking-Water Quality in New Zealand

Water quality gradings from the 2006 Register of Community Drinking Water Supplies

Our report on water and your health

Our report on water filters

Our report on water quality

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