Water hardness depends on the amount of calcium, magnesium or other minerals are dissolved in the water.
|
grains per gallon
|
mg per L (parts per million, ppm)
|
Water Hardness
|
|
0 - 1.0
|
0 - 17.10
|
soft
|
|
1.01 - 3.5
|
17.11 - 60.00
|
slightly hard
|
|
3.51 - 7.0
|
60.01 - 120.00
|
moderately hard
|
|
7.01 - 10.5
|
120.01 - 180.00
|
hard
|
|
> 10.5
|
> 180
|
very hard
|
where:
• 1 grain per gallon = 17.12 mg per L
• 1 grain = 64.7989 mg; 1 gallon (US) = 3.7854 liters
• The exact limits of the water hardness table may vary between different sources.
