[MaxxxRacer]

Im not saying that and I never did. that is obviosly incorrect. You are just twising my words around.

Its obvious when the tubing is horizontal (never is in our case) that the restriction comes from tube D and friction inside of the tube and friction between the water molecules. since its horizontal the water would flow out slowly by itself due to the fact that there is no cap on the end of the tube, but after a certain lenght, the pump itself would not be pushing the water out. it would just be flowing out itself from gravity. (after a certain head point, pumps auto-shut-off)

Now lets say the tubing is vertical. Then the weight of the water does come into play. at that point the pump is having to push the entire column of water that is in the tube up to the head (lets say there is jsut a tube that sprays off into oblivion). That is the way head is measured. And its entirely due to the weight of the water. At a certain point the water is too heavy for the impeller to push it upward.

Again, you and I both know that its stilly to say the thing Diameter tube will have higher flow. higher exit velocity when exiting the tube but no more flow. obviously less flow. hence wider is better (to a point)