1.Wilson, Amber; Parrott, Kathleen; Ross, Blake (1999-06).
“HouseholdWater Quality – Water Hardness”
2.Briggs, J.C., and Ficke, J.F.; Quality of Rivers of the United States,
1975 Water Year — Based on the National Stream Quality Accounting
Network (NASQAN): U.S. Geological Survey Open-File Report
78-200, 436 p. (1977)
3.Mean hardness as calcium carbonate at NASQAN water-monitoring
sites during the 1975 water year. Colors represent streamflow from
the hydrologic-unit area. Map edited by USEPA, 2005. Modified from
Briggs and others, 1977.
4. USGS, http://water.usgs.gov/owq/hardness-alkalinity.html
5. Data obtained from testing using a GE Nautilus DishWasher set on
Pots and Pans setting, water tested using LaMotte Hardness Test Kit,
Liquid Version, Code 4482-LI-01.
6. Sanitation Districts of Los Angeles County – Press Release,
Feb. 25, 2003
7.Water TechnologyMagazine, May, 2002:
For those who measure hardness as PPM, here is the conversion
1 mg/L = 1 PPM(Parts Per Million)