Hello to All: I will be setting up an EKO 25 with storage (300 to 600 gallons) unsure at this point. The water volume of the boiler is 20 gallons. Something that I would like to dial in on is pump sizing for the flow to storage. My plan is to have the boiler to storage and back as primary loop. Although there is a couple of tons of info on this site, I see nothing directed at this. The information provided with the boiler does not address this. So I figured I would just compare to other brands and find similar instances. Came up empty. Certainly each sized boiler and the size of storage would have different requirements. Has anyone thought this to be worth consideration? My thinking says that too fast is not optimum as well as too slow. Are there programmable controllers that would alter the output of a variable speed pump in operating to optimize btu transfer rates? My first thought is to use a Grundphos 3-speed and implement a trial and error period.