Christchurch City Council will consider temporarily chlorinating its water supply after engineering assessments revealed some of the city's wells may be susceptible to contamination.
The council waited a month to make public that the Canterbury water assessor removed the city's secure bore status last month.
Christchurch's drinking water is drawn from 156 wells located at 56 sites across the city.
The Canterbury Medical Officer of Health, Alistair Humphrey, has advised the best option is to temporarily chlorinate the water, which the council will consider at a meeting on Thursday.
He said flooding was one way the water could become contaminated.
Council spokesperson John Mackie said there was no current issue with the quality of the city's ground water and it was safe to drink. The council said the engineers' assessments raised concerns that some of the below-ground wells may not be sufficiently sealed to prevent surface groundwater contamination, particularly in heavy rainfall.