I've pored over water softener sizing information for the past week. For what it's worth, I'm a chemical engineer by profession and am having a little trouble making the right conclusions.
Here are the specs:
- Hardness - between 185 and 242 mg/L (as reported on two different tests; I used the higher value).
- Iron - none
- Manganese - none
- pH - 7.3
- Family of three (maybe 4 eventually) with high water usage (wife and I shower in AM and bathe in PM, lots of dishes and car washing); no special fixtures.
- House with kitchen sink, scrub sink, 2 baths (1 shower, 1 tub), clothes washer, dishwasher, and three hose bibs.
- Water is supplied by well (25 years old) - pressure between 35 and 60 psi - flow measured at bathtub around 10 gpm (if I remember correctly).
A vendor spec'ed me a 32000 grain system but suggested I could upsize to 40000 grains. Suggested was a Fleck 2510 at 40000 grains because of the 1" internal valve (1.25 cu ft resin).
Gary Slusser's calculator confirms about 27000 grain system but suggests a 1.5 cu ft softener size. Not sure if this is resin volume or softener size, but this would suggest a 48000 grain softener if it's resin volume (the 30K setups I've seen are 1.0 cu ft, 40K are 1.25 cu ft).
Where I get even more lost is at the SFR calc (and I have studied Gary's page)... If my well is putting out about 10 - 12 gpm, I'm somewhere between a 1.25 and 2.0 cu ft unit per Gary's page. If I add up all my fixtures and randomly pick a plumbing code to determine SFR sizing, this has me at 2.0 cu ft+.