PMID 17710278. ↑ A multicentre randomized controlled trial of ion-exchange water softeners for the treatment of eczema in children: protocol for the Softened Water Eczema Trial (SWET) (ISRCTN: 71423189) http://www.swet-trial.co.uk/ ↑ "Water Hardness". thekrib.com. 1 2 USGS - U.S. Geological Survey Office of Water Quality. "USGS Water-Quality Information: Water Hardness and Alkalinity". usgs.gov. ↑ Total water hardness ↑ Corrosion by water ↑ T.E., Larson and R. V. Skold, Laboratory Studies Relating Mineral Quality of Water to Corrosion of Steel and Cast Iron, 1958 Illinois State Water Survey, Champaign, IL pp.