[selchie]

It sounds as though rural areas rely on rainwater rather than well water, n'est pas? Interesting. I wonder what the groundwater situation is. It does seem as though with rainwater all kinds of fun stuff can find its way to your tap, so that filtration would be a minimum precaution to take.

I'm not sure how it goes in NZ, but perhaps folks could find a private water (or environmental) testing lab to have some basic analyses done. It would cost some money, but could help with peace of mind and perhaps health. Testing for coliform bacteria would be a minimum, with perhaps metals analysis, depending on the roof. If it's galvanized, test for zinc.

I think I'd be buying bottled water if I had no knowledge of the water quality in the cistern.