Can this tell me whether my water is safe to drink?
No. It is a sizing and planning tool. Use your utility CCR or an appropriate certified laboratory test for water-safety questions.
Is ppm the same as mg/L for hardness?
For practical water hardness conversion, ppm is commonly treated as approximately mg/L. The planner expects hardness as mg/L (or ppm) expressed as CaCO₃.
How many mg/L are in one grain per gallon?
About 17.1 mg/L as CaCO₃, based on USGS field documentation.
Why does the softener calculator use 75 gallons per person?
Penn State Extension uses 75 gallons/person/day in a softener sizing example. The dedicated calculator lets you change the assumption.
Does high iron mean I should buy a bigger softener?
Not automatically. Iron treatment depends on concentration, form, pH and product limits. The planner flags iron above EPA secondary guidance for additional evaluation rather than adding a made-up hardness factor.
Do I need a whole-house filter for city water?
Not necessarily. Municipal water is already treated and regulated. A whole-house filter should target a specific goal such as taste/odor, sediment or a verified reduction claim.
Do I need UV on a private well?
Not automatically. UV addresses microbiological treatment; the need should follow well testing, source conditions and professional/local guidance.
What does NSF certification mean?
It means a product has been evaluated to a particular standard and claim. It does not mean the product reduces every possible contaminant.