My quiestion is if you have several grow beds, can you run all of the drains back into a single pipe? The system I am starting will have 7 (98sf) grow beds and 2 300 gallon fish tanks. I am just curious before I spend the money on clay pebbles.
I think you can. I have 6 draining into one tube. Think my flow would be about 1100 GPH to my 6 beds, 120 ft2. Probably much higher than yours will be. I did use 4" tube though, I tried 3" first. As TC said earlier, "the bigger pipe costs more but it costs more yet to buy the 3" and later pull it out and buy the 4". The 3" might work for you depending on your flow.
I think you can. I have 6 draining into one tube. Think my flow would be about 1100 GPH to my 6 beds, 120 ft2. Probably much higher than yours will be. I did use 4" tube though, I tried 3" first. As TC said earlier, "the bigger pipe costs more but it costs more yet to buy the 3" and later pull it out and buy the 4". The 3" might work for you depending on your flow.