@DracoKat you might like this...
History
The problem that the Durso is there to supposedly correct is TOO MUCH FLOW.
What's Going On
A 1" gravity drain is rated for 600 GPH....that's the peak/most it will carry.
When you get anywhere close to that limit, you start getting noise just due to siphons starting to form and then breaking within the gravity drain.
The partial siphons suck all the water out of the drain box, causing sucking sounds followed shortly by waterfall sounds as the drain box refills, etc.....
You're lucky if you don't also have bubbles and gurgling noises coming from your sump too....generally you get both effects.
People have come up with all sorts of innovative ways to get closer to or exceed that 600 GPH drain limit (Maggies, Durso's, Stockman's, Bean Animals, Herbie's, etc, etc, etc) without going insane from the bubbles, noise and salt creep. (The part we didn't even mention that can damage your property).
More History
The thing is, there once was a good reason for all that motivation and innovation to get more and more through your drains:
Your tank needed flow! Powerheads of the day stunk at making flow in a big tank.
Today, there is no good reason....we have propeller pumps for flow. End of story.
So How Much Flow?
With the burden for flowing the main tank lifted, that leaves our return pump just needing to run the filters and keep the skimmer fed.....which amounts to 2x to 4x your display tank.
Quite moderate requirements - actually what most drains were designed for. Gravity drains are supposed to be near-silent by nature.
So, if you have a 100 gallon tank, anwhere from 200 to 400 GPH would do the trick.
You might argue for 500 GPH just because performance on the pumps and plumbing tend to degrade somewhat ofter time, but more than that would more or less be a waste and just turn into noise and bubble problems that need to be solved.
