The max capacity of a softener requires 15 lbs of salt per cuft of resin in the softener.
Originally Posted by Wally Hays
Now let's say there are 2 people in the house and there is 10 gpg hardness in their water. 60gals per person per day*2 people = 120 gals/day of water use on average. 120 * 10 gpg hardness = 1200 grains of capacity used per day. 1200 * say 8 days between regenerations = 9600 grains rounded to 10K.
Let's say they can use a 9 gpm SFR 1.0 cuft softener. That means you can program for 10K by setting the salt dose to 3.0 lbs per regeneration which would equate to 10,000/10 gpg = a meter setting of 1000 gals between regeneration (yes that's without a reserve) or..... 1000gals/120 gals/day use = a regeneration on average once every 8 days.
Set the softener to the max of 30K in a 1 cuft softener which requires 15 lbs of salt per regeneration and... 30,000/10 = 3000 gals/120 gal/day use = 25 days between regenerations (WAY TOOO LONG for good resin life) BUT, if you look at 30,000/15 lbs we see the salt use (salt efficiency) is 2000 grains of capacity per pound. And the right way of 10,000/3 lbs shows you are getting 3333 grains per pound or, we are using tons less salt than the 30K setting is using; 6 lbs in 24 days compared to 15 lbs every 25 days.
A 1.0 cuft softener is usually called a 32K. Regardless of the brand name or cuft size, you lose 2K of regenerated capacity per cuft of resin the first time you use new resin; it can not be regenerated.
So your 32K becomes a 30K, 64K is a 60K, 48K = 45K etc. etc. ONLY IF you salt dose at 15 lbs/cuft of resin.
Which is a salt efficiency of 30,000/15= 2000 grains/lb. It's like terrible fuel mileage caused by you just having to be in the passing/left lane passing everyone you can with your foot in the flue injectors from one stop sign or red light to to next, then you complain about all the fuel your Subaru uses and swear you''ll be the first to buy the Government Motors (GM) VOLT as soon as they hit your local dealership.
Capacity calculation: # of People times 60 gals/person/day (or whatever gallons you think but 60 is usually right on) + all extra softened water use in gallons/day; IE horses etc. multiplied by the compensated hardness = total grains/day. Grains/day * 8 (days) for a once every 7-9 days regeneration (if less than 5 ppm iron; 4 days if you have over 5 ppm of iron) plus a day of reserve capacity (not needed for twin tank models or the Clack WS-1 CS version) = the total grains of capacity you need. Then from the chart below find the capacity at the best salt dose that covers your total grains needed. With twin tank softeners you must subtract the total gallons used per each regeneration because they use softened water for the regeneration.
Example: 3 people *60 = 180 + 10 gals/day for a horse = total 190 gals/day, * 19 gpg compensated hardness = 3610 total grains/day. Then 3610 * 8 days = 28880 total grains needed which should be rounded up to 29 or 30k. Using the salt dose capacity chart below, you find the volume of resin that produces 29,000 or 30,000 grains of capacity using 6 lb/cuft of resin. That gives you great salt efficiency and covers your capacity requirement. As long as the constant SFR gpm of that size softener is correct, you have a properly sized softener with great salt efficiency. If your peak demand gpm is greater than the constant SFR gpm for that size softener, you would use the size the constant SFR dictates and then adjust the salt dose and thereby the capacity.
The 6 lb/cuft salt dose gives you 3333 grains of capacity per lb of salt used rather than the maximum salt dose per cuft of 15 lb which generates only 2000 grains of capacity per lb of salt. If you use potassium chloride instead of regular softener salt (sodium chloride) and you are using low salt doses (say 8 lb/cuft) below, you have to increase the salt dose by roughly 27-30%.