A Wellington City Council report suggests the city's water and sewerage infrastructure would suffer badly in the event of a 7.5 magnitude earthquake.
Most of Wellington's water comes from three treatment plants, and pipelines cross the Wellington fault at least twice.
The report found those pipes could take up to 66 days to repair fully, and the best-case scenario is that water supplies might last for only 20 days.
The council's civil defence controller, Mike Mendonca, says consideration is being given to stockpiling chemical toilets, to cope with inoperable sewerage.
He says discussions are being held with the Government and other councils about where stocks could be held.
Mr Mendonca says councillors will look at the report and decide what improvements need to be made.