Hard water is normal around here, and it quietly costs you. Scale on the fixtures, spots on the glasses, more soap than you should need, and a shorter life for everything in the house that heats water. Supply, installation, servicing and repairs.
It looks out of place next to furnaces until you follow the water. Nearly everything in the house that heats water is where hard water does its damage: the tank, the heat exchanger in a tankless unit, the loops in a floor, the kettle, the element in the dishwasher. Scale is an insulator, so a scaled element has to work harder and longer to do the same job, and it gives up sooner.
That is the real argument for a softener, and it is not the one usually made. The soft skin and the clear glasses are pleasant. The reason it belongs on a plumbing and heating card is that it protects the expensive things.
