if water is being moved, whether by circulation pump or filtration, the water is still being moved. Why not count this? do you not count the water in your filtration? I am confussed, I thought this was all part of the whole?
I used distilled for a long time with better results than NSW. Wal-mart 83cents a gal. I bought anywheres from 20-50 gal a week, they loved me, LOL. If you don't have your own RO/DI, I say distilled is the best choice. Also, most distilled jugs have the info on the distillery.
Take all of this with a grain of salt and not personally.
First and foremost: You should as a practice look at filtration as filtration and flow as flow.
You do not count it because the flow is uni directional, not aimable and it's primary purpose is NOT flow to transport the nutrients to your corals. It's only true purpose is to move water from point A to Point B for processing. This is just generally accepted in this hobby as the way to look at things. You can look at it any way you want, because you either have enough proper flow or you don't.
Now the Distilled water thing. Take your TDS meter down to your store and run it on the "distilled water" and let me know your results. Now go and run it on a self maintained RO unit let alone a full RO/DI unit. Point proven.
Now lets move onto your argument that you had better results with the distilled water than with NSW. Can I ask where you got the NSW? If from a public aquarium where did they get theirs? How far off shore, distance to the nearest brackish area, and geographical runoff in said area, along with in land businesses and factories situated on the natural run offs.
Now lets say you harvested your own seeing as you are in NY and it is FEASIBLE....
What type of mechanical filtration did you do? Light deprevation cycle? Chlorine and chlorine neutralizer used, UV filter applied, how many sand/ charcoal beds did it run through? Did you test for the trace minerals required by TROPICAL reef systems?
There is A LOT of work that goes into harvesting NSW as you can see and i barely scratched the surface.
I am not trying to be mean or speak down if it came across that way, but rather show that there is a significant difference.
Also in regards to the flow not including filtration it really only has to do with a manner of organizing characteristics of the tanks systems by functions.
P.S.: You bought 20-50 gallons a week at .83 cents. So say 44 bucks rough in head calculation on a large purchase week. You can get a 100 GPD 5stage water general unit with pressure gauge and dual DI for 125 shipped.