it`s been MY experience in a N.F.T. system to run the water all the time, but i`ve seen other similar systems run their solution through the tubes 15 minutes to one half hour every hour or 2.
either way would work, but i preffered to have the solution run 24/7 with solution changes every week, and system flush every month to wash out accumulated fert salts on inside of res. and tubes.


hope this helps you out