It is best to purchase an inexpensive digital timer to handle the floods, since they allow you to program better flood times. The optimum flood is just long enough to allow the flood to reach the correct flood depth, plus a few minutes to allow the nutrients to wash thru the planters, carrying away accumulated salts from the planters. Try to have the total time not exceed twenty minutes if possible, and never allow it to exceed thirty minutes total time.
With the megagarden for example: The system reaches desired flood depth in less than four minutes and drains away in about five minutes, so a ten minute flood allows pleanty of time and finishes the task in roughly fifteen minutes total.
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