Max throughput of flow through RSB/HO

[Delphinus]

It seems there could be a potential flow threshold for the Red Sea Berlin skimmers. That is, a point at which any increased pressure does not really increase any flow through the unit.

If this is true, anyone have any estimates of what this could be?

The reason I ask is, I am trying to estimate my tank volume turnover rates. I actually have no idea what it is, reason being is that my sump return is feeding both my sump return AND my skimmer. But it stands to reason if a person could estimate how much flow there is through the skimmer, subtract that from the pump's rated flow rate at given head pressure, and that should give me a theoretical maximum flow rate for the sump return water.

I'm kind of tempted to divert the main tank's overflow into a 5g bucket, and time how long it takes to fill that, at least that would kind of give me a rough idea what my sump turnover is...