Map the problem
Note where hardness shows up
Walk through the bathrooms, kitchen and laundry area and note what you find: scale on faucets and showerheads, soap residue in tubs and sinks, or detergent that seems to work poorly. Include water-using appliances and the water heater in the list.
Concerns spread across several rooms point the discussion toward whole-home softening. A problem limited to one fixture may have another explanation, so mention that too. The pattern helps separate hardness from a single faulty fixture.
