Quick take
A 9 GPM system can work for modest demand, but 11–12 GPM service flow gives more margin for a three-bathroom household. RKIN CS9 and SpringWell CF4 sit in that higher-flow zone.
Why bathroom count is only a shortcut
A three-bath home with low-flow fixtures can need less capacity than a two-bath home with a large rain shower and fast-fill tub.
9 GPM vs 11–12 GPM
SpringWell CF1 is 9 GPM service; CF4 is 12 GPM. RKIN CS8 is 9 GPM service while CS9 is 11 GPM. The larger tier gives more headroom for overlapping fixture use.
Peak flow matters
RKIN also publishes peak ratings, which can help compare brief high-demand events. Continuous service flow should still be the primary sizing number.
Connection size
Most mainstream systems in this range use 1-inch connections, which is useful when the home already has a 1-inch main line.