Difference in pump operating point for open/closed end pipe

Hi All,
I have a question that I couldn't get an answer for it till now.
If I have a pump with a known characteristic curve at the upstream end of a piping system. And if the piping system at its end discharges water to a tank (closed end) or to the atmosphere (open end). I know in the closed end, I have to draw the pipeline system curve and intersect it with the pump curve to get the operating point which may be different than the rated discharge and head of the pump. How about the open end case?
[B]Do I have to work with the rated pump discharge and head regardless of the pipe system since there is no control from the downstream?[/B]

The problem I am solving has a pump curve (1 design point, Qr = 65 L/s and Hr = 19 m) and the pipeline is Polyethylene 7000 m long with inner dia. = 500 mm.

Please, can anyone help on that.
Thanks...

I think what you try to explain here is very confusing. For me, your closed end and open end is the same open circuit. It is differ than close circuit system as in chilled water system. In pump operation, no matter where your design point is; it still has to extend to meet pump curve.