Chlorine is expected to be out of Napier's water supply by the end of the month.

Today marks a fortnight since the city's water supply was chlorinated, after a positive reading for E. coli was returned at one of the Napier City Council's Park Island sites.

The positive reading was 1, the lowest level possible. Anything under 1 is classed as safe to drink.

Although there have been no further positive E. coli tests returned during daily testing across the network, chlorination has continued as a way to disinfect the pipes.

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Yesterday the council's manager asset strategy, Chris Dolley, said the supply would be chlorinated for a total period of three to four weeks.

As the chlorination began a fortnight ago, it is expected to continue for another week or two.

A secure chlorine dosing site had been established in Taradale, injecting chlorine into the reticulated system 24 hours a day. With the exception of Otatara and Puketapu, all of Napier is being chlorinated.

Mr Dolley said they would determine the chlorination was no longer necessary when they had stable residual chlorine levels across the network. This was being monitored on a daily basis.

While there has been some negative criticism online Mr Dolley said overall there had been support from the public that the council acted quickly, and put "the top priority on public health outcomes".

This is the second time Napier's water has been chlorinated - in February the city's water supply was chlorinated for a period of 12 days after the Enfield Rd reservoir returned a positive E. coli reading of 1.1.

Given the high number of transgressions recently, the council had begun rolling out a series of planned improvements to the entire water network.

Mr Dolley said this was a "comprehensive" programme of work which would look at operations, maintenance and capital improvements, and would take several years to deliver in full.

Improvements would concentrate on modifying or completely overhauling the testing points - the places where water was drawn for regular testing.

Sample points were being reviewed to ensure that they are properly located to provide a clear indication of the water quality of the public water supply, he said, and that these were dedicated sample points with no other use.

While some residents have complained of a "swampy" smell and taste of the water, council have advised this is not harmful as it was caused by the chlorine cleaning the pipes as it washed through.

This was not harmful, and could be fixed by running a tap for between five and 10 minutes. If this continued, residents were asked to call the council's Services Team on 06 8357579 to flush the nearby hydrant in the street affected.