Pump on sump tank help

[Buckshot41]

I have 100 gallon tank! What size pump do I need on my sump tank! I know on a canister filter you need at least a 400 gph! Thanks

[mr_X]

What are your overflows rated for and are they HOB or built in?
What exactly will be going in the sump? Your skimmer and heaters? How many gph is your skimmer pump?

[Buckshot41]

Have a DIY overflow 1/2 PVC pipe!

[mr_X]

1/2" pipe? That's definitely not going to be enough.

[Buckshot41]

Should I go to a 3/4 or 1" then? If so what size pump do I need?

[mr_X]

I don't know the ideal gph for the different size pipes, but I know they use a 1" drain on a 800gph overflow box, according to a quick google-
CPR Overflow Boxes
That should answer your question about pump size. You will need to have a pump after head loss that will match your drain.