Nearly one in six drinking potentially unsafe water

File photo / The Aucklander

Drinking water flowing to almost one in six New Zealanders either failed to reach Ministry of Health (MOH) standards or escaped testing during 2007/08, the ministry says.

It has released its annual drinking water quality review , conducted by the Institute of Environmental Science and Research.

About 91 per cent of the population get their water from a town supply while the remainder have their own supplies - generally from their roof or a bore - which are not monitored.

The review found 8 per cent of New Zealanders are on town supplies which have not passed testing for bacteria and viruses.

MOH principal public health engineer Paul Prendergast said the indicator tested for was the bacteria E.coli.

"E.coli in the water doesn't necessarily make you sick, although some E.coli can. It's just telling you you've got faecal matter in the waterway and if that faecal matter is from a sick animal with a waterborne disease then that could pass through to humans."

A further 15 per cent of town supplies have not passed testing for cryptosporidium, which can lead to an upset stomach.

The ministry found most large communities had good supplies but in areas where the population dropped, compliance tended to go with it.

Of particular concern were the 590 schools and early childhood centres with their own water supplies.

Only 421 did any monitoring and of those just 103 passed tests for bacteria while none was cleared of cryptosporidium - a failing attributed to their use of ultraviolet treatments which were believed to be inadequate.

There were 10 hospitals with private water supplies and these all passed bacterial testing, but, as with the schools, most were unable to eliminate cryptosporidium.

Nationally, access to certified clean water increased 3 per cent when compared to the previous year, but the ministry said it was alarming to see 38 instances where contamination was found in water supplies run by local authorities but had not been remedied.

Mr Prendergast said those cases would be checked up on.

The report also noted a small number of suppliers who were not reporting failed results, even after repeat testing confirmed contamination.

When viewed regionally it appeared Wellingtonians were drinking the cleanest water with the Hutt Valley (which supplies much of the region) providing 100 per cent of the local population with faecal matter-free liquid.

Auckland was at 98 per cent while Canterbury only managed 88 per cent.

The West Coast posted the lowest score with only 57 per cent of its residents receiving their water without potentially harmful additives.

- NZPA