For your application I would recommend a 2 Cu. Ft. 7000 programmed to 6 pounds of salt per cu. ft. This will give you an estimated 15 days between regenerations, and it will also handle the high flow demands of the three bathrooms. I can send you the programming cheat sheet once you have purchased your system. You can really minimize the water usage from the 7000 easily without sacraficing longevity or quality.