Water Hardness by US region map

As a follow up to a user question in our "Removal of water scale buildup from water heaters" article I did a bit of digging around and found this map on the US Geological Survey's Water quality web page.


Source: (USGS Water-Quality Information: Water Hardness and Alkalinity) Accessed 2010/02.

This map shows data from 1975;

The range classifications for water hardness are as follows

Note this is based on amount (milligrams per liter) of calcium carbonate
SOFT - 0 to 60 mg/L
MODERATELY HARD - 61 to 120 mg/L
HARD - 121 to 180 mg/L
VERY HARD - Greater than 180 mg/L

It makes me wonder if detergent manufacturers take these regional water hardness variations into consideration when planning what products to sell in the various states.