Hard Water Regions of the USA

In the USA Water hardness is often broadly classified in bands of hardness as follows:
0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft
61 to 120 mg/L as moderately hard
121 to 180 mg/L as hard
180 mg/L and over as very hard

Geographically, more than 60% of the USA suffers from hard or very hard water. The quality of drinking water in the USA is normally good, but it must be remembered that the only statutory obligation on the Water Authorities is to supply water fit for potable (drinking) use. This puts no obligation on water authorities to be concerned in any way about the hardness of the water. Hard water can be potentially corrosive and damaging to domestic appliances, pipework and central heating boilers. An Eddy descaler is often an effective protection against the problematic effects of hard water.

Map courtesy US Geographical Survey

Water hardness measurement conversion chart