Drilling an overflow and return

Hey folks,
Backstory - I have a 55 gallon reef tank with hang on back everything and maintenance has been a nightmare. I am now switching to a sump/ refugium set up and I am DIYing my new set up.

I will be using an extra 55 gallon tank for drilling and a 20 gallon long for my sump. The overflow has to be drilled on the back (the bottom of my tank is tempered) I have a reef octopus 4" protein skimmer and an Eheim compact 3000 for my return...my question is - what size hole should I drill for the back of my tank for 600 gph flow?

Thanks in advance for your help

 

An 1" hole will be sufficient

 

An 1" hole will be sufficient

I disagree.

A 1" bulkhead and plumbing will be sufficient for 600GPH (1" can handle about 960GPH with gravity pressure)

Depending on the brand of bulkhead, the hole size required will be different, but I believe most 1" bulkheads use 1 3/4" hole (1.75", or 4.45cm).

I'd suggest buying the bulkhead first (for 1" plumbing), and check the hole size required

 

Also plan on the style overflow you will be doing. 2 holes for Herbie method and 3 holes for Beananimal method.

 

Thank you everyone ... Your information has been very helpful. I am going through BRS for the bulkhead & they have a recommended size for the drill

Again thanks