550 GPH with 1" PVC overflow?

[soggysandwich]

but you have to take bends and other restrictions into consideration. If it's a DIY overflow I would make 2 1" ones to flow that much just to be safe.

agree, the more the better! the last thing you want is an over flowed tank. plus if one stops working for what ever reason you have a back up

 

[CHOMPERS]

so if you have an overflow of 1 1/4" how many gallons per hour does that do? and what size pump do you need to keep up with it?

1 1/4" will flow twice what a 1" overflow will = 1200 gph.

The overflow needs to flow more than the pump.