One pump is a Reeflo Dart for sump return, the other would be a GenX/Mak4 (assuming it still works, it should, it's just been shelved a few years), which would drive the skimmer (beckett). The GenX should be better able to push against head pressure and wouldn't be throttled; the Dart will likely be throttled but I'm not sure how much will be needed until I fill the tank and see how things settle out.
The Dart has a 2" inlet port and the bulkhead is 2". The GenX on the other hand has a 3/4" inlet port.
My worry is that one pump's suction could be perceived by the other pump much the same as a blockage or throttling on the input side. I know that throttling the outlet side of a pump is copesetic (it's just head pressure); but that throttling the inlet side of a pump is a no-no
so was sort of curious if two pumps pulling out the same pipe could produce a similar effect, or if it just creates a wicked suction into said pipe via the bulkhead...
Thanks for the thoughts..