From seeking cylinder failure reports via facebook.com/CashmereNZ/posts/832075763590531,
Richard Howard, soil and groundwater consultant of Separate Phase Ltd, says:
Beckenham water is known to be hard. The CCC may dose it with lime to prevent pipe corrosion, but this is a balancing act for them as lime clags up all the hot things like your jug and pipe work. We installed a Bosch gas system and they last about 5-7 years in these conditions. Much easier to replace than a cylinder.
Christchurch Water 