What this tool does
Converts hardness to grains per US gallon, applies only the iron compensation factor entered by the user, and separates working capacity from reserve-adjusted capacity and service-flow review.
When to use it
Use after a current laboratory test and before comparing the exact manufacturer capacity at a stated salt setting and service-flow curve.
Inputs and supported units
Each labelled field explains the quantity it expects. Unit-system changes convert existing numeric entries once and keep calculations on a single SI internal basis. Supported shared units include L/min and GPM, metres and feet, kPa and psi, millimetres and inches, kW and hp, and °C and °F as relevant.
Calculation or decision method
The conversion used is 1 grain/US gal = 17.118061 mg/L as CaCO₃. Iron allowance is added only when the user supplies a factor from applicable product or technical data.
How to interpret the result
Read the primary result with the supporting breakdown and warning. A plausible number is not evidence that every input, operating case or design constraint has been included.
Worked example
171.18061 mg/L as CaCO₃ is 10 grains/US gal. At 1,000 L/day for 7 days with 20% reserve, the preliminary reserve-adjusted capacity is about 22,190 grains before any user-entered iron allowance.
Assumptions
The entered water test, flow, product concentration and manufacturer values represent the same source, use and operating condition.
Limitations
The result is a transparent preliminary calculation or decision screen. It does not establish contaminant removal, potable safety, product certification, regulatory compliance or an approved treatment design.
Sources
- U.S. EPA WaterSense — Cation Exchange Water Softeners
- U.S. Geological Survey — Water Science Glossary
- NSF — Standards for Water Treatment Systems