I am to do some "water equalization" tests outside with a garden hose on that trickle (wet/dry) to simulate how it would actual drowning down into the 20 gallon sump vs along side of it. Probably quieter next to it, but I agree with the socks. Would filter pads do more/less the same thing? I calculated the FULL volume of the overflow to be 6.89 gallons at the most. So even if all of this drained into the sump then I can't see any risk of it flooding. And that wouldn't happen because the durso or other drain pipe would be at least halfway up. Makes me question if I should even do the herbie vs just the 1" as a durso and then could Y the return pump to the two 3/4" bulkheads as returns.
I have never had a saltwater weir setup so I don't have any reference to advise you by on the amount of settled overflow you will get. I think your plan of running some tests with a garden hose is a great idea! Do you have a return pump you can use to model the whole system in action? A more powerful pump will keep a bit more water "in action" in the system giving you a bit more settled overflow.
I am, of course, introducing my own preferences into my recommendations for your sump. I would definitively use filter pads on top of the trickle chamber for the bulk of the mechanical filtration. You want to remove the solid waste out the water before the water is introduced into your sump. My thought on adding filter socks to where the water enters the 20g (if feasible) was for water polishing. If the filter pads (course on top finer underneath) above the trickle chamber removes 99% of the solids fine mesh sock filters between the two sumps would be a nice way to polish the water and remove that last 1% of cloudy.
I am a bit of a clear water freak! I like REALLY clear water in my tanks. I use a full time DE filter to keep my water perfectly clear. Fine mesh socks are another way to polish the water nearly as well with less hassle than a DE filter.
