Approximately, when the dissolved rocks comprise more than 50 parts per million, the water is considered 'hard'.
The average rive can be 300 ppm, and some water can reach 1000 ppm.
Rain water is around 10 ppm, and yes, its beaut to shower in.
To soften the water, the trusty tried and proven method is a, wait for it. a WATER SOFTENER
These function simply by washing the water through SALT.
When the salt runs out, you need MORE. These are BIG systems - a pressure tank can be 1800 x 300 mm.
HRV has been found guilty misleading claims - of selling a very small metal device THAT DOES NOT WORK.
So don't be fooled with fancy new products that have no independent verification of performance claims.