A malfunction at a Western Bay of Plenty water plant is believed to be the cause of an "incredibly unusual" warning issued to residents yesterday not to drink or use water.
The warning was issued to Pukehina Beach residents yesterday morning after the Western Bay of Plenty District Council received two complaints, including a report of a woman suffering a rash after taking a shower.
The council launched an investigation and soon extended the warning to include the Paengaroa, Maketu, Little Waihi and Pongakawa areas before flushing the supplied water systems.
Water tankers and bottled water were delivered to all the potentially affected areas, which took up to six hours. By yesterday afternoon the water supply to Pukehina was back to neutral pH but the council recommended people flush their system for 10 minutes before drinking or bathing.
Pukehina farmer Errol Watts said his wife told him of the water warning but he was left unsure of whether the high pH would affect his work.
"My concern would be, as a farmer, we use our water to wash down sheds and there's such tight regulations, we don't know what we should do. That would apply to every dairy farmer out there, and there is a lot."
Council utilities manager Kelvin Hill said people should try rubbing their fingers together in the running water and if it felt slimy to the touch, to then keep flushing. Water cylinders were to be flushed completely and households with header tanks are advised to do the same.
Other areas such as Paengaroa, Maketu, Little Waihi and Pongakawa were expected to be given the all clear overnight and residents would be notified by the council.
Mr Hill said it was a timely reminder for people to keep an emergency supply of fresh drinking water as part of their household emergency plan.
Chief medical officer Dr Phil Shoemack said water with a high pH level reflected a high alkaline level, whereas a low pH level had a high acidity level.
Dr Shoemack said both ends of the pH scale could be highly irritating.
If someone attempted to drink water with high alkaline, they would likely spit it out because it would be so unpleasant and irritating, Dr Shoemack said.
"At the extreme, a very high pH level would be something like caustic soda and can burn the skin. This water was nowhere near that high but that gives you an idea of what impact something with high alkaline can have."
It is understood a malfunction at the plant prompted the water issue.
Dr Shoemack said the incident was "incredibly unusual".
"We are very fortunate that virtually every part of New Zealand, council drinking water supplies are incredibly reliable. If things do go wrong, systems are in place."