You dont need a test kit, just look in your kettle. If its white inside, the waters hard, if not it soft. I live in a hard water area, and I use a softener for my t/m. Its not one like you would use at home, fully automated, its basically a round tube filled with resin and connects into the fill line.you manually flush salt through every 1000 litres. I did not like the idea of every flushing every 2 or three tank fulls as I dont always empty the tank before re filling. So I installed a small water meter into the fill line and also a solenoid valve connected to a level sensor. So I can now fill whilst cleaning, having a cuppa or whatever and know exactly when to back wash the softener. Can be bought from Hydramaster.