How many gph does my tank drain ??

I am setting up a 175 bowfront tank. It has dual drilled overfows with bulkheads that currently taper to a 1 1/4" drain. (Doesnt seen right to me I asume I can get bulkheads that will allow for more flow)

I am just trying to determine how fast water will drain out of this baby to so I can maximize the flow.

Any assistance would be most helpful.

Thanks!

 

Not sure on how to determine from the size of the drain holes,but I think most has to do with the rest of the plumbing and pumps as well.
This article may help, I found it helpful.
How To Determine GPH Water Flow Rates of Saltwater Aquarium Pumps and Filters


\Cheers

 

Thanks for the help.
I just want to make sure I get a pump with enough coconuts to handle and maximize the flow. I am using a rubbermaid sump and I want the tank to drain freely. I am also considering adding a second pump to the rubbermaid to push water to a closed loop set up above the tank for flow.

I just need to determine the maximim drain rate.

Thanks man!