Twin tank softener size calculation
I have read a lot in this forum about sizing for single tank but not very clear for twin tank. I am interested in a twin tank 9000 for a 3 bathrooms house, with washer and dishwasher, now we have 2 people but may become 4-5 in couple months. Our city report showed ~ 10gpg. I was thinking about 1.5cuft/tank, total 3cuft running at 5lbs salt dosage = 22000 gr./3500gr.(fr 5 persons x70x10) = 6.3 days x2 ~12 days in between generation. But if only 2 person this could go 22000gr./1400gr.(2x70x10) = 15.7 x2 ~ 31 days in between generation for each tank. Should I just go one tank instead? Could the experts help checking my calculation?
Thank you very much!