Herbie drain capacity and emergency drain

[Reefstarter2]

So I am not sure this is the correct place to post this , if not I appologize . My question is this .... well maybe a little explaination first . I am setting up a 210 gallon tank , it has a single overflow on one end that hase holes drilled in it for one 1 inch bulkhead and one 3/4 I want to use a herbie style drain to keep it quiet should I use the 3/4 as main and 1 inch as emergency ? or the other way around . and what would the flow rates of either set up be ? I have been searching for a simple answer online all over the place and there are so many variables tossed in I am confused lol. I should also add that I will be using 1 inch ID braided vinyl hose down to the basement sump to minimize bends and hopefully get what I want for flow . ( around 700 GPH ) I know this is considered a bit low by standars . but in tank flow will be plenty enough. Thanks in advance for responses . Happy reefing

 

[Reefstarter2]

drilling the tank is not an option either

 

[stingeragent]

https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml

There is a calculator somehwere that I can't find that lets you put in the head height, number of 90's, 45's, etc and it spits out the flow rate. If you wanna be on the safe side, use your 3/4 as the main drain and 1" as the backup. If you wanna improve flow, use the 1" as the main, and 3/4 as a backup. Keep in mind if doing that, if your 1" drain 100% clogs the 3/4 won't be able to keep up unless your return pump is under 660gph roughly. (when I say 660, I mean after head loss, etc)