Hydrion Water Hardness Test Kit (packed with two rolls of test paper 0-20 grains per gallon and 10-50 grains per gallon) Hydrion Water Hardness Test Kit (packed with two rolls of test paper 0-20 grains per gallon and 10-50 grains per gallon) For accurate results; simply tear off a strip of test paper, immerse in water for five seconds, compare color to color chart.