Mostly. Tap water is safe to drink in urban areas — but it isn’t safe to drink the water everywhere in New Zealand.
When you’re in more isolated areas, always check for any signs saying that tap water isn’t drinkable (potable). Boil, filter or chemically treat water from lakes and rivers before drinking to protect yourself from Giardia — a water-borne parasite that causes a nasty gastric condition.
If you’re planning plenty of hiking, consider purchasing a water filter. Most good outdoor stores sell them.
Find out about motorhome water basics to avoid contaminating your onboard drinking water.