Size of sump return section?

[fishyfun2]

Hello,
How do I know how big to make the return section of my sump? DT is a 29 gal and sump is a 20 gal. I would like to incorporate a small refugium too, so trying to save space for that, but also I want to be able to leave town for the weekend and not have my pump go dry!
Thanks!

 

[natclanwy]

Are you going to have a skimmer in the sump? If so a 20g is not really big enough to incorporate a fuge and skimmer and still leave enough room for evaporation in your return section. Without the skimmer I would split the tank in half use half for the fuge and half for your return.