2 - 1" Overflows Enough?

[Jaws]

So I'm going to be returning approximately 1000GPH to my main display from my sump. I have two 10 linear external overflow boxes that are drilled for 1.5" bulkheads. The rest of the plumbing is 1" and I'd like to use 1" pvc for the overflows as well for a couple different reasons. Will two 1" overflows be enough? Any worries of clogging with only 1" overflows? Thanks in advance.

[Palster]

I had asked a similar question quite some time ago. I seem to remember reading that 1 inch plumbing will handle about 600 GPH and 1 1/2 inch plumbing will handle about 1300 GPH. Having two 1 inch overflows would be marginal and according to these calculations would handle 1200 GPH which would mean that if one of your overflows was to become clogged the other overflow would not handle the flow and possibly result in a flood. I ended up going with two 1 1/2 inch overflows on my previous tank for that reason. Have a look at my original thread.
http://www.canreef.com/vbulletin/showthread.php?t=31041

[Sebae again]

On my CPR overflow, I have 2 1 inch pvc overflows with 1 inch valves adapted to 1 1/4 black flex sump hose for ease of sump/equipment service.On one section ,I used clear 1 1/4 tube to see what flow was like.There is still ample room for water. On the return I have 1 inch pvc in and out of a Mag 12. The 1 inch is equally split into 2 3/4 lines which inturn are slit into 2 1/2''lock lines. No problem with blockage and no throttling of valves was required.