The Christchurch City Council says the water reservoir in the Huntsbury Hills area is empty and there is no danger of flooding for residents living below it.
Some residents have reported hearing sloshing noises coming from the reservoir during aftershocks but the council says that is not possible because there is no water in it.
The reservoir is damaged and cannot hold water.
The 37,000 cubic metres of water that was in it when the earthquake hit ended up in a nearby river through the pipe system.
Jeremy Kelleher, who lives next to a reservoir in the Huntsbury Hills, says residents heard the sloshing of water during the frequent aftershocks and he was eager for it to be inspected.
Mr Kelleher says there would be a huge cascade of water if a side blew out and says there are hundreds of houses below it.
The Lyttelton reservoir has been confirmed as having suffered damage.