Switching from Canister Filter to Sump System

[MoshDmM5]

I'm relatively new to the hobby so bear with me. I have a glass non-reef ready 90 gallon tank currently running on a canister filter and a hang on back bio wheel filter. I am wanting to change fully over to a sump, of which I have a used one that I am assuming is a 25 gallon sump. The dimensions for it are 17"H x 25.5" L x 13.75" D. I am currently working on getting the back of the tank drilled to avoid having to do a HOB overflow. I've done a little bit of reading around and I've found that the turnover for a tank this size would approximately be 900 gph; according to the calculator, I would need a drain @ 1.24" and a linear overflow @ 14" to handle 900 gph. Also I'm not quite sure what size bulkheads I will be needing for a tank this size. Any help will be greatly appreciated!

 

[laverda]

Realistically modern thinking is about half that is ideal. Some people even say 25%. If you aim for 550 GPH a 1” drain line will handle it. With a second emergency drain of 1” or 1.25 for extra safety. 2 One inch bulkheads or 1 one inch and 1 one and a quarter inch.
Many people like to use 3 drains, but I never saw the need. It is easy enough to make your drains quite with 45 degree fittings. Your overflow can be reduced to 10” safely.