What is Soft Water?
What is soft water is a relatively easy question to answer. Soft water does not have the common qualities of hard water as defined by the WQA (Water Quality Association) below. By observation soft water is water that is easy to work with. Simply stated: Soft Water does not behave hard.
Please note: everything in italic blue text below comes directly from the WQA web site.
Below is an snippet from the blog Hard Water Defined.
"Hard water is a common quality of water which contains dissolved compounds of calcium and magnesium and, sometimes, other divalent and trivalent metallic elements. The term hardness was originally applied to waters that were hard to wash in, referring to the soap wasting properties of hard water. Hardness prevents soap from lathering by causing the development of an insoluble curdy precipitate in the water; hardness typically causes the buildup of hardness scale (such as seen in cooking pans). Dissolved calcium and magnesium salts are primarily responsible for most scaling in pipes and water heaters and cause numerous problems in laundry, kitchen, and bath. Hardness is usually expressed in grains per gallon (or ppm) as calcium carbonate equivalent."
The part of the definition to focus on and keep in mind is how the term hardness was originally applied. This is what maters to consumers of water. It describes water quality behaviors consumers observe, how water containing untreated minerals (dissolved calcium and magnesium) behaves.