Christchurch City Council is warning residents that because of earthquake damage they need to conserve water.
Although the water supply was restored shortly after the September quake, the council says, it remains compromised and may not be able to handle peak demand over summer.
The council says 10% of wells in Christchurch are unusable and another 40% need of repair or redevelopment.
It expects supply to be fully back to normal in 18 months. In the meantime, residents must conserve water or restrictions will be put in place.