Boil water notices have been placed around the Martinborough town square. PHOTO/HAYLEY GASTMEIER

Backflow issues at private properties could be the cause of Martinborough’s second E.coli outbreak in months, which prompted a boil water notice to be put in place last Tuesday.

South Wairarapa District Council’s acting chief executive Jennie Mitchell said investigations into the contamination continued to be focused at the reservoir as well as private connections with the mains water supply.

She said some Martinborough residents and plumbers had come forward with information about potential backflow issues at private properties, where water could have flowed back into the mains supply.

“We’re keen to hear from anyone who might have information about faulty or missing backflow prevention mechanisms, particularly where there are connections to water tanks or other water supplies.

“There will be no negative consequences for property owners coming forward,” Mitchell said.

Backflow prevention mechanisms should be installed to all connections to prevent this from happening.

Martinborough water is vulnerable because unlike most town water supplies in New Zealand, it is not chlorinated.

A UV disinfection system is used to treat the water at the point of entry into the system, providing a single barrier of protection.

Mitchell said a “multi-barrier approach” would be required to ensure safe drinking water for the future.

“It’s essential that we identify and address all the possible sources of contamination.

“The boil water notice cannot be lifted while there is ongoing risk of recontamination within the network.”

Test results from samples taken on Wednesday showed no signs for E. coli as the areas that previously showed contamination had been chlorinated.

The boil water notice remains in place and residents are advised to boil all drinking water for making up formula, juices, ice, washing fruit and vegetables, and other cooking needs, or brushing teeth.