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Water softener size calculator
Household size and water hardness to the softener capacity you need, with iron compensation for well water.
Grains per gallon
Hardness test kits report grains per gallon (gpg) or parts per million (ppm); divide ppm by 17.1 to get gpg. Water over about 7 gpg is hard enough to leave scale on fixtures and shorten water heater life.
How the size is worked out
A person uses about 75 gallons of water a day. Multiply people by 75 by the hardness, and you get the grains the softener removes each day. A softener sized for about a week between regenerations uses salt and water efficiently.
New Hampshire wells
Many wells in the Monadnock Region also have iron, manganese, low pH or arsenic. A lab test first tells you whether you need a filter ahead of the softener. See water filtration.
Common questions
What size water softener for a family of 4?
With 12 gpg hard water, a family of four removes about 3,600 grains a day, so a 32,000-grain softener regenerates about once a week.
Does iron affect softener size?
Yes. Each ppm of iron counts as roughly 4 gpg of hardness. High iron often needs a dedicated iron filter.
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