Be aware that the build-up occurring could be calcium or silica. The water softening devices that have been around for a long time cannot cure a silica build-up.
Last year I was talking to a lady about scale build-up on bathroom fittings in the Western Bay of Plenty. She was adamant it was calcium (lime) scale and wanted a system that "would remove calcium" as she was moving into a gated community and wanted good clean water that didn't mess up the shower glass. I tried to explain that there was little (if any) problem with calcium scale in the area and she really needed a system that would address silica scale.
Silica scale is a well known problem throughout many parts of NZ, especially in the Bay of Plenty and is often (in ignorance) mistaken for lime scale. Silica is virtually impossible to remove from glass once it has formed a molecular bond, which is almost instantaneous once the water evaporates leaving the silica in direct contact with the glass. Glass is made from silica and thus they form a powerful bond under the right circumstances. The only 'in-line' filter that we have personally seen reduce the nasty effects of silica (other than RO - which is expensive and slow) is the KP Water 'Ionizer'. It has a unique design that uses rare earth magnets to produce a very strong 'focused field'. Our happy customers have reported that this reduces the appearance of lime scale. It was designed & developed here in Tauranga, initially to reduce lime scale, but over the last few years we have modified the design for use in areas with silica scale.
Unfortunately, the lady above has information from sales people who cannot 'fix' silica and therefore label it 'calcium' so their own system looks like the right choice. She proceeded to inform me I "knew nothing about the water here,,,, and also the local council had said it was calcium". However, that is possible as local councils are not necessarily well informed on technical matters and sometimes just repeat what they've been told.
Fortunately there are many people who realise that most sales people actually do care that their customers get the right advice and the right product. We want ongoing business, preferably by 'word-of-mouth', because the recommendations come from our customers