Maybe I shouldn’t be trying to calculate flow rate but just finding the correct performance curve? Is there anyone out there who can provide the curves for the pump I describe in tis thread? The performance curves given here: http://www.pentairpool.com/pdfs/stariteoptifloDS.pdf only go down to ¾ HP but I need the data for ¼ HP. Even with the curve, what formulas should I use to compute the total head?

Appreciate any help I can get, as I won’t buy the heater until I know if it will work with my system.