return and drain hole sizing.

[Fairymary58]

OK bare with me I've just worked 4 nights straight and I can't think straight to save my life right now.
What size drainage and return holes would a 12 foot need?
I was thinking 50mm drain and 40mm return (aussie sizing) or have I got that the wrong way around?
Or is there something else you would recommend?

 

[laverda]

You want your return to match your pump output generally and your drain at least one size bigger as it will not have much pressure even as a full syphon. You really want at least 2 drain lines to avoid issues.

 

[Saltees]

Your drain should be at least 1 to 2 size bigger than your return. Eg. 1” drain 1/2” return.