I am trying to decide on the best size water softening system for our home. There are 3 people using approximately 200 gpd, 3.5 baths, 7.5 gpg compensated hardness, potential for peak flow rate to reach above 9 gpm.

I have been researching how to best determine what size unit to purchase and am still in a quandary and need to replace our system soon. From my recent research, I understand that for our consumption pattern and our well water condition, if I get a 1.0 cu ft unit using a Fleck 5600SXT and set it to use 6 lbs of salt, it will regenerate approximately once a week. This would seem to be an efficient use of salt and would be good for the resin's performance and maintenance. I would need to accept that if we occasionally exceeded the stated peak or maximum service flow rate of the resin, that hardness will break through. From what I understand, 1.0 cu ft of 8% crosslink resin can handle a maximum service flow rate of 9 gpm. If I wanted to get a higher max service flow rate of 12 gpm, I would use 1.5 cu ft of resin, and using a 6 lb salt setting would use 9 lbs of salt per regen but this would not regen within the optimal timeframe for a healthy resin bed and would lead to channeling. So, I assume I would need to set the override on the Fleck to regen every 7 to 8 days and I would be using 9 lbs of salt per week instead of 6 lbs for the 1.0 cu ft unit in order to get a higher service flow rate thus potentially avoiding hardness breakthrough. I would be using more salt and more water to regen the 1.5 cu ft unit. This would not be an efficient use of salt or water to get a higher max service flow rate but would be necessary to maintain the resin bed properly and to potentially avoid hardness breakthrough.

Sorting through all the information and opinions on the internet and from local water conditioning professionals to come up with an answer to the question "what salt setting should be used if I want to regen every 8 days and use salt efficiently and effectively for a 1.0 cu ft unit?

For a 1.25 cu ft unit?

For a 1.5 cu ft unit?

consuming 1400 gallons of water in 7 days with a compensated hardness of 7.5 gpg?" has been a real challenge.

I will probably be going with a 1.0 cu ft system using SST-60 resin (for its potential higher flow rate capabilities and salt efficiency), set to regen using "X" amount of salt ((to be determined)(any suggestions)) with the override set for every 8 days. I understand that if I exceed the max SFR of "X" (7 gpm? 9 gpm? still researching) that hardness will breakthrough.

I had a comprehensive water test from a certified independent lab done for the water from the well and one for after the existing softener, a week ago. The compensated hardness number I used to estimate what size system I would need is 7.5 gpg (6.5 gpg hardness + 1.0 for .01 mg/L iron). The pH is 6.7. I understand that the pH is a bit low but will not add a neutralizer at this time. I rounded the 7.5 gpg off to 8 and the water consumption is rounded off to 70 gpd per person. I calculated that 210 gpd X 8 gpg X 8 (7+1 for reserve)days between regenerating = 13,440 grains to be removed. I rounded this off to 14,000 to estimate that I would need 1.0 cu ft of resin to remove the hardness from our water. The problem is that 1.0 cu ft of resin may not be able to remove the hardness when our maximum flow rate exceeds the resin's capacity. So, I would like to know if a 1.25 cu ft system or even a 1.5 cu ft system would be more appropriate.

I was guessing that using SST-60 with a less than optimum sized system would support higher flow rates with less salt and water consumed for regenerating, even though iron is not a concern. I will be installing the system myself and the SST-60 is available locally for approximately $30 per cu ft more than standard 8% crosslinked resin.