Oh, right. Guess that is one of those terminology questions. So that would be the total length of the surface of the overflow box, including sides?

Not sure what you mean by "including sides".

Perimeter of the whole box? Hmmm. Good question. I'm not sure but I think so. If it meant just the length, like I thought, then you'd be lookin' at a 71" long overflow box for 4,700 GPH. Seems kinda big, but 4,700 GPH is big too.

I'm sorry. I'm gonna have to plead "I don't know" on this.
:redface:
Danny?......

Cheers,

So if it is perimeter why wouldn't they just say overflow surface area instead of linear overflow size. You're right. It is very ambigous. I think I'll shut up on this one now and let some who hopefully knows the answer help ya out. :redface:

Cheers,

Linear size is the total length of the area water flows over. So a 6"x6" corner overflow box is 12" linear length. How they calculate for tooth size escapes me though.

Ok thanks. Time for me to do more research on closed loops, sumps, ect as I plan out my system.