What size drain pipe will you be using for your growbeds?

I suspect that drain size effects cycle times greatly. I currently have 3'x8'x1' growbeds with gravel median, and used 1 1/2' drain pipe. My cycles per hour were way too many, as my water volume had to be high to produce a syphon with such large pipe. Also, with such large pipe, it has a really strong syphon and drains really fast, starting the cycle even sooner. But, I am testing this theory this weekend.