I was alerted to your ongoing conversation regarding the water quality in Cashmere and wish to add my experience.
I live at 125 Bowenvale Avenue and had a rebuild 2 years ago. My house was fitted with a Peter Cocks Silver bullet hot water cylinder and required two replacement elements within 6 months. I was advised to purchase a sacrificial anode and last week both were in a serious state of corrosion requiring replacement as once again I had no hot water.
I welcome your investigations and am concerned as the hot water cylinder in my original house did not suffer this fate for up to 2 years following the earthquakes.
Post-EQ Cashmere cylinder failures