Updated September 22, 2026
Iron, manganese and water softener sizing
Hardness load and contaminant treatment are different questions. A larger grain number alone does not prove a softener can handle iron or manganese.
What the iron adjustment does
Morton’s selection guidance specifies adding 5 GPG per ppm of ferrous, dissolved iron for its softeners. Our calculator uses that as an explicit screening convention, not as evidence of another brand’s iron-removal capability. Ferric, particulate iron needs a different assessment.
Example: 10 GPG hardness and 1 ppm dissolved iron gives 10 + (5 × 1) = 15 GPG effective hardness. At 300 gallons/day, that is 4,500 grains/day and 36,000 grains for the eight-day scenario. Without the iron adjustment, the same scenario is 24,000 grains. The 12,000-grain difference is calculated. It is not a product performance claim.
Manganese is outside the numerical calculation
No manganese value or multiplier is included. Known or suspected manganese requires a separate product and treatment assessment. Do not enter it into the iron field, combine it with hardness, or interpret its absence from the inputs as evidence that it is harmless or treatable by a catalog softener.
EPA’s private-well guidance recommends iron and manganese testing when considering softening. Give the results to the equipment supplier and obtain model-specific treatment limits and any pretreatment requirements.
What water source changes
Choosing private well changes warnings and prevents a standalone catalog shortlist. It does not add a hardness multiplier. Enter the measured chemistry either way. Positive iron also pauses the standalone shortlist. A blank iron field never silently becomes zero.