I’m just learning about the IAPMO Water Demand Calculator. Has anyone been using it?

It looks like it uses Hunter’s Curve, which as we have been saying for decades now, overestimates. But that is code in most locations. So our recommendation is, design to the code, but understand that you already have 40% redundancy. Don’t add any more! And make sure that the pump you select can handle the low flows. Pressure tanks help this, a lot!