You must be referring to 1/2 ID, which is how tubing is measured. Seven ft. is fairly short, so you should be able to get sufficient flow (volume) through that size tubing with not too high p.s.i. You can test your system by pumping water through it into a 5 gal. bucket and timing the event with a clock second hand, to get the gal/per/minute flow. No need to dig out your fluid dynamics college text and use your scientific calculator to get viable results.
Use an electric eccentric vain (positive displacement) pump and you will have plenty of flow. Such an item should be available from your local marine supply house.
The biggest consideration in flow resistance is the tightness of the tubing bends. Fluids don't like to go around corners! Ninety degree corners are the worst. Over the years I've seen such right hand corners in fuel system fittings and it just makes me cringe. At least the specialty fuel line makers have rounded 90* connections and hose ends.
Also, another serious restriction in a hose system is the fitting that the hose goes over. For years, hot rodders have been drilling such fittings to a larger diameter. Make sure that any fitting you use has at least a 1/2" hole, which may require some heating (with very hot water) to expand your tubing to get it fitted. If you use regular 1/2" heater hose, this won't be needed, as it will stretch enough to fit.
It might help us to help you if you were to tell us what you are trying to do. Sometimes there are fellows out there who have attempted/done about the same thing that you are trying to do. Then there would be no need to "re-invent the wheel", you see.
