You don't have drains, you have balance pipes. Balance pipes are only worthwhile at extremely low flow rates, because there is no gravity advantage. As someone else mentioned, the tanks need to be seperate, and stair stepped so there is a gravity advantage "tank" to "tank". With the current setup that is not possible. Hence this setup will never work right. Additionally, multiple gravity feeds such as you would need to use, will never balance out right, as no two drains will ever operate exactly the same. Therefore it is a flood waiting to happen.
The only hope of getting it to work, are seperate discrete drain lines, one from each "tank" or "section" all the way to the sump, and seperate feed to each tank from the return pump. That way water in will always equal out. Hence no flood risk, save for a clogged drain, which of course would make for a nice flood.
