Definitions for

**"Grains Per Gallon"**A unit of measurement often used to describe water hardness. One grain per gallon is approximately equal to 17 ppm of various cations.

A unit of measurement still used in some North American water analyses. One grain per US gallon is equivalent to 17.12 milligrams per liter.

A unit of concentration equal to 17.1 milligrams per liter (17.1ppm). Commonly used as a measure of hardness in water.