Sump design, why so many chambers?

[jorjef]

Okay this is sounds good. I'm trying to re-define the K.I.S.S. design to the overflow and sump but must be flood proof. The sump will likely be the existing 77 gallon display which is being replaced with a 150. I had some advise to have two 1.5" drains, one main, one emergency and decided on just one return.