Choosing an overflow(drilled)

[Wfduncan89]

I am setting up a 30 gallon long innovative marine with 20 gallon sump. I am trying to choose an overflow box and I am looking at the modular marine 800 gph and 1200 gph. I haven't chosen a return pump yet. I'll ideally have two return outlets on either end of the tank (the tank being 35ish inches long). I would imagine the 800 gph would be more than enough to handle 2-5xor whatever I want turnover, however The 800 has 1/2 inch drains and the 1200 gph has 3/4 inch drains...My main concern is how 1/2 vs 3/4 inch plumbing will work for me. Should I have any concerns/considerations? Any reason to go one over the other?

 

[Quietman]

This chart has been around for years. The overflow boxes will handle it but the drain pipe might be limiting factor.

 

[bradreef]

As long as it has three pipes for drains. I would go with the 800 which it looks like it does. That will ensure you off silent overflow.

 

[Kodski]

The modular marine 800 gph would be plenty. 10x turnover is only 300gph which you’ll be fine with for 1/2” pipe. I’d be more concerned about 3/4” pipe causing issues with trapped air and siphon start problems.