Quake-damaged water and waste systems have so far withstood the freezing conditions in Christchurch.
Underground infrastructure is undergoing a rebuild following the February 2011 earthquake and concerns have been raised about what impact the freeze and thaw would have on pipes that are already cracked.
Christchurch City Council water and waste manager Mark Christison says the thaw is causing twice the volume of water to flow through the storm water network, but the treatment plant in Bromley is holding up.
The normal flow through the plant is two-and-a-half cubic metres per second. On Thursday, it peaked at five cubic metres per second.
Mr Christison says most of the water pipes and sewers are below freezing level, but the council is keeping a close eye on them.