From this link:http://www.aquatell.com/canada/knowledg ... r-softener
This link from that link is also very informative about sizing.
http://www.aquatell.com/canada/knowledg ... r-capacity
Apparently weekly regen is about right to keep the machine running without things starting to 'stick', keeps the parts moving. I've read it elsewhere.
"Now Calculate the Daily Softening Requirement
Multiply your daily water use by your water hardness (corrected for iron). This number is your Daily Softening Requirement. Here's an example:
Hardness: 10 grains per gallon
Daily Water Use: 4 People X 75 Gallons per day = 300 gallons per day
Daily Softening Requirement = 10 grains per gallon X 300 gallons per day = 3000 grains per day
In the example above, the softener will be removing 3000 grains per day. A softener is usually sized to regenerate about once per week"