Job was done by Aquaheat Hasties Joint Venture.  JV is now dissolved.  Don't think there is any question of a problem with the installation - the copper involved was Crane Copper and some has already been replaced with Kembler copper (small amounts).   There is a lot more to this than meets the eye, the question of a lack of filters, water quality etc - it doesn't appear to be anywhere near as simplistic as simply poor quality copper.   One thing's for sure - it is going to cost the taxpayer of NZ a shit load to rectify.