If it's not a kink, the pipe could be air locked- a bubble of air in the pipe that presents enough resistance for your low head not to be able to shift it against the resistance of the pipe. Try reducing pressure at the ballcock end- suck on it (though this could be a long haul with a long pipe)- you'll have top do it in stages, blocking the end with your thumb between sucks. Or rig up a hand pump to pump it out by lowering the pressure at the end.

Or try working it out- raise the pipe at the tank end, then walk along forming a travelling wave with the high point, the idea being to get any air bubbles to the end of the pipe. You'll have to be careful that the pipe in front is always higher, otherwise the bubble will just go back.