Water System Sizing

Residential water treatment calculator

Find the right water softener size for your home.

Estimate the grain capacity your household needs using water hardness, daily use, and dissolved iron—before comparing products.

01

Your water and home

Enter what you know

Changes treatment guidance and product screening, not the grain-load calculation. Private-well systems require a separate water-chemistry review.

Screens product bathroom ranges—not grain load.

Converted value: — GPG

ppm

Enter a measured value, or explicitly enter 0 for a no-iron planning scenario. Leaving this blank does not assume zero. Unknown iron needs testing before product selection.

Manganese is not included in this calculation. Known or suspected manganese requires separate product and treatment assessment. There is no manganese multiplier here. Iron and manganese guidance

— gal/day75 gallons × — people
02

Sizing result

Your estimated requirement

Start with your water and household

Choose a water source and enter people, bathrooms, hardness and dissolved iron. Your estimate will appear when the required entries are valid. Blank values are never treated as zero.

Before choosing a system

Common sizing questions

Where do I find my water hardness?

Use a hardness test or ask your water utility for a hardness result. Enter hardness as calcium carbonate, not total dissolved solids (TDS). A TDS meter does not provide the hardness value this calculator needs.

Should I enter my entire water bill?

Use only the water expected to pass through the softener. Exclude irrigation and other bypassed outlets. The 75-gallon-per-person default is an editable planning estimate, not a measurement of your home.

Why is working capacity lower than the grain label?

Capacity depends on resin and salt dose. Manufacturer manuals list different capacities at different salt doses. The result is a working-capacity requirement, not a nominal grain label. Ask the supplier for capacity at the intended salt setting. See the calculation and sources.

Does a bigger softener solve low water pressure?

Not necessarily. Grain capacity and service flow are separate checks. Bathroom count screens product ranges. Pipework, pressure loss and simultaneous fixtures still need review.

Know before you buy

A sizing estimate, not a water-safety test.

Water hardness is mainly an appliance and usability concern. This calculator cannot detect bacteria, lead, arsenic, nitrates, or other health-related contaminants. Private-well owners should use certified laboratory testing and qualified local advice when selecting a complete treatment system.