Quick take
Choose CF1 for 1–3 bathrooms and modest demand; choose CF4 for 4–6 bathrooms or when 12 GPM service flow provides useful margin over CF1’s 9 GPM.
CF1 specifications
SpringWell currently lists CF1 for 1–3 bathrooms, 9 GPM service flow, a 9-inch tank and 1-inch connection.
CF4 specifications
CF4 is listed for 4–6 bathrooms, 12 GPM service flow, a 10-inch tank and 1-inch connection.
When a 3-bath home may still prefer CF4
High-flow showers, frequent simultaneous use or a desire for more flow margin can justify CF4 even before the home reaches four bathrooms.
Media capacity is not the differentiator
Both current models are marketed around 1 million gallons / 10 years of media life, so the practical sizing difference is primarily flow and tank size.