WATER QUALITY - Hardness of water March 22, 1962 QUALITY OF WATER BRANCH MEMORANDUM NO. 62.47 To: District Chiefs and Staff Officials, Water Resources Division From: Chief, Quality of Water Branch Subject: WATER QUALITY - Hardness of water We have had no uniform policy in classifying water hardness by numerical ranges or adjective ratings. This subject again came up in connection with manuscript preparation for reports on public water supplies of the United States. Country-wide, there is need for standardization. After discussion with field and Washington staff members, I am establishing the following breakdown, which will henceforth be used where hardness classification is discussed: Hardness range Adjective rating (ppm) 0-60 soft 61-120 moderately hard 121-180 hard 181 + very hard Because hardness grouping is of interest to many offices of the Division, copies of this memorandum are being mailed to all field installations. S. K. Love WRD Dist: A, B, S, FO.