How does protein skimmer vertical return pipe (stand pipe) work?

[zeroinverse]

Maybe this is a newbie question.

I have seen in-sump protein skimmers that only have one "vertical standpipe". They do not have a T-pipe to create the vent/standpipe and the elbow to point downward for water return.

In these vertical return pipe, does the water simply return back into the protein skimmer chamber?

Doesn't this cause the protein skimmer to "reskim" the same water (of course whatever baffle you have set up in the sump will eventually overflow and move this partially cleaned, partially dirty water to the next section.

It seems this is less efficient than the ones with the "T-split" to immediately put skimmer water into the next section.


Was not sure how to find the answer and I am trying to design my sump around a protein skimmer that has the vertical standpipe configuration (with no Tee'd elbow.)