Lukew,
You must work in the Brisbane area, as Sydney, Melbourne, Dubbo, Adelaide, Perth, and just about everywhere else I have visited in Australia has soft, to very soft, water. The water in Brisbane is hard by Australian standards, but is very soft compared to the water in most of the industrial area of Germany. Hardness readings of twenty grains per gallon are not uncommon there and while many German printers use a RO system, most mix the RO water half and half with their tap water to get between eight and ten grains per gallon.
You posted this nice report postulating that water hardness has no effect on printing, yet you admit to using a water hardener, what benefit do you see from this? Does your water hardener use calcium, magnesium, or some other hardening material? We manufacture a water hardener for those customers we have who are required by their press manufacturer to use one, ours is made from magnesium acetate. Why printers are willing to pay extra for a water hardener escapes me, when their fountain solution manufacturer could incorporate the hardening ingredients into the fountain concentrate without changing the cost of the fountain solution by more than a few cents per gallon eliminating the freight cost and mixing issues an extra solution bring into the picture.