In December, the Drinking Water Assessor advised the Christchurch City Council water supplies were no longer secure due to the degradation of below ground well heads.
City services general manager David Adamson said minimal doses of chlorine would be added while two thirds of the city's well heads were replaced or repaired.
He said although we have very good groundwater "of excellent quality," public health has got to be paramount.
He said residents would not notice a difference in taste once chlorine was added to drinking water.
"We are going to be using very low dosages [of chlorine], so we are hoping people will notice absolutely nothing different in their water".
He advised residents with fishtanks to "fill up drums of water and let them sit for 24 hours as the UV in the sun evaporates the chlorine".
Canterbury Medical Officer of Health Dr Alistair Humphrey said: "While we like the taste of our untreated water, it is important that we keep the water safe."
"The vast majority [of residents] would rather have a safer water supply than a water supply that might put them or their families at risk."
Dr Humphrey believed the Council had "come to the right decision to keep the water safe until such time as the engineers can sign off those bore heads, which we estimate should be around about October".
David Adamson said chlorination would continue until the well heads are secure.
More information, visit the Christchurch City Council website.