28 May 2018

Christchurch council to reduce chlorine levels in water supply

6:43 pm on 28 May 2018

Christchurch City Council will reduce the level of chlorine in the city's water to try and fix the smell and taste issues raised by locals.


Water Photo: 123RF

The council began chlorinating the water in late March after finding that some below-ground well-heads could become contaminated during heavy flooding.

But many Christchurch residents complained, saying their water tasted like a swimming pool.

Council general manager of city services David Adamson said others believed treating the water had caused or worsened skin problems.

"Obviously people that are susceptible to things like eczema have found that, because of the drying nature of chlorine, it's dried their skin out further and exacerbated that problem for them."

The council now planned to reduce the chlorine dose at 27 pump stations where the water took at least two minutes to reach people's homes.

The concentration would change from one part per million at one minute to half a part per million at two minutes.

"Chlorine operates as a dosage or a concentration versus time, and so half a part per million times [and] twice as long is the same level of protection," Mr Adamson said.

Council experts were hopeful the change would fix the issues people had raised but could make no promises, he said.

"They believe it's worth trying. They believe that certainly there's a good chance it will deliver benefits but they cannot guarantee [it]."

The other 26 pumps would still get the higher dose of chlorine until alternative measures could be put in place.

Public health was paramount but the council had a range of strategies to reduce the overall chlorine content in the city's water, Mr Adamson said.

There were currently three pumps that did not require chlorination at all and the council hoped to use these and the lower dose pumps as far as possible across the network.

"So we're looking at putting them on the main duties so that they will put more water into the network than others, so that's certainly part of our strategy."

Other options included upgrading the well-heads and flushing water pipes with high pressure water to clear out organic material, which contributed to the strong chlorine taste.

In the longer term, the council would consider treating the water with ultra-violet and ozone.

It was still the council's aim to reach a point where there was no chlorination in the water but it would depend on the government's response to the 2016 Havelock North gastro outbreak inquiry, Mr Adamson said.

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