The chlorination of Christchurch's drinking water is almost complete.
Water Photo: 123RF
In December last year, the council revealed that some below ground wellheads could become contaminated, especially during heavy flooding.
It voted earlier this year to install temporary chlorinating equipment at all of the city's 56 pump stations.
This week, those serving the majority of the city were treated.
Next week wells providing water to the remaining 11,500 residents in Ferrymead and Lyttelton would be chlorinated.
Council spokesperson Dave Adamson said chlorine would be removed from bores progressively as they were each made secure.
"I don't have to get them all signed off to start turning down some of the chlorine or turning off some of the chlorine. The council at the moment has got a resolution giving the staff permission to chlorinate for up to 12 months and if it's going to be longer than that we will need to go back to council."