Grain (Water Hardness)
Unit of dissolved calcium and magnesium: one grain per gallon equals 17.1 ppm. US water runs from soft (<3.5 gpg) to very hard (>10.5). Softener capacity in grains = people × daily gallons × hardness × days between regenerations.
Where this appears in real estimates
This term isn't trivia — it's a working variable. These tools use it directly:
- water softener size calculator — Softener grain capacity from household size, usage and hardness.…
Go deeper
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- Related engineering article — from our licensed engineer
Reviewed: · Part of the CalculatorAsphalt Construction Glossary · Sources: see methodology & standards.