I need help in sizing a water softener. The Hardness is 17gpg, 3/4” water service on City water, no Iron and 2 full bathrooms. The problem is we are a family of 5 and when the kids are away at school we are 2. Daily water use can be anywhere on average from 133 gal to 288 gallons a day. I thought I had it all figured out using a Fleck 5600SXT, 1.5 cubic foot of 10% Purolite C100E resin until I got the last water bill showing 12,000 gallons used for the quarter when it was normally 26,000 gallons. I don’t want to over think this but I want to make sure it’s sized right. Thanks for your help.