Waikato's Medical Officer of Health this morning issued a health warning for the water supplies at the King Country community of Benneydale.
Heavy rain yesterday damaged the filtration process at Benneydale's water treatment plant.
The source water is muddy from rain over the past few days, and thetreatment process is no longer removing suspended material.
Disease-causing bacteria, viruses and protozoa has washed off surrounding land and is contained in the suspended organic material.
All water for drinking, food preparation, and brushing teeth must be boiled to be safe, said Dr Dell Hood.
Benneydale is a community of about 500 people 36.5kms south east of Te Kuiti, where a warning was imposed last weekend due to contamination of the source by a local meat works plant.
Dr Hood had not received any reports of illnesses at Benneydale, although it was still too early for negative effects to have taken place in affected people.
"The incubation time for chryptosporidium and giardia is about two to three days, and even campylobacter can take some time so the earliest we would see effects is 24 hours."
Benneydale had gone through similar problems "off and on for sometime" so residents may not be reporting illnesses, she said.
"It could be that they're dealing with it at home, so we would not necessarily know unless we went out looking for the information."
Chlorine disinfection would kill bacteria and viruses, but filtration was needed to remove the protozoa (cryptosporidium and giardia).
Benneydale's water is chlorinated but due to the absence of filtration the water is not safe to drink.
Boiling for one minute would kill all disease causing organisms, Dr Hood said.
After boiling, the water might still be taste unpleasant and appear brown, but it would not spread disease.
Emergency supplies of clean, safe water are being arranged for Benneydale people by the Waitomo District Council.
Using the town's water for washing laundry, showers and cleaning would be safe, and would not spread disease, Dr Hood said.
The Waikato District Health Board yesterday lifted the health warning on Te Kuiti's water.
However, the ban could be reinstated if ground at the meat works becomes unstable.
