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Table 3 Water hardness classification

From: Coastal sand dune ecosystem services in metropolitan suburbs: effects on the sake brewery environment induced by changing social conditions

Hardness classification USA hardness (ppm)
Soft water 0–60 less thana
Medium hard water 60–120 less thana
Hard water 120–180 less thana
Very hard water 180 or morea
  1. aWorld Health Organization (2011)