[MaxxxRacer]

I know flow rate is the same through the entire loop. I have never contested that. In the end if the components are in series then the flow rate will be the same.

All im talking about and have been talkign about is pressure not flow rate. there is some other component to this that I dont quite understand, but the pressure will be higher before a highly restrictive block than after it exits. Im not talking about flow, just the water pressure itself. The Psi before the block will be higher than after the block. Thats all that I am saying. Sadly it would be really hard to measure this.

Even though water is not compressable the psi force that water is exerting does change. In a submarine when you go deeper the psi changes. the water doesnt compress, but it tries to compress everything else. Now do you see how the pressure can drop as the water flows through the system.

I know it seems odd as the flow stays the same at any given point through a closed loop (my sytem isnt entirely closed as i have a res)

here is a point to think about. when the water gets to the res in the system the pump is no longer forcing the water out of the res, but is sucking the water out of it. if it was pushing it through the res rather than sucking it out, the res would be completely full all the time. if i open the top on my res the res doenst overflow and that is becuase the water that is flowing out of the res is being SUCKED out by the pump. NOT being PUSHED out. Granted since i have my res above the pump gravity would take effect if i unhooked the pump, but u dont exactly get alot of flow using gravity.