Backflow issues at private properties could be the cause of a second E. coli outbreak in recent months, which has again prompted a boil water notice to be put in place. 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. The chief executive reports that 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.
The borough is interested in who might have information about faulty or missing backflow prevention mechanisms, particularly where there are connections to water tanks or other water supplies. 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.
Ms. Mitchell said authorities were looking at a multi-barrier approach which would be required to ensure safe drinking water for the future. She stated that it is 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 the most recent samples taken 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.