Additional Resources:
Fill-in-the-Blank Monovalent/Divalent Cation Ratio Calculation Form download
EPA Softener/Septic Factsheet
EPA Septic Smart Website
NOWRA/WQA Guidance Document
Softeners and Septic Performance Toolkit

News Releases:
April 2013: Major study suggests efficiently run softeners do not hurt septic tank performance
June 2011: Study launched to look at softener effects on septics
March 2011: Studies show washing with softened water can significantly cut detergent use, energy consumption 
April 2010: Independent study: Softeners among 'very best' household energy savers