This article is from the New Zealand FAQ, by Phil Stuart-Jones and Lin Nah with numerous contributions by others.
NZ cities and towns have good public water. Water is safe to drink out of
the tap. The water in Christchurch *is* totally untreated and is supposed
to be the purist domestic water supply in the world...
In bush walking areas giardia has been found so its advisable to check
before drinking from rivers or streams. Boiling water for five minutes or
more is advised where advice is not available.
 
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