For the past 16 yrs I've used 3 sump pumps in a hole with 10' of head & I've always put the check valve right at the pump, in the sump hole. I'm guessing that I saw that setup when I installed the first one & have just copied it since.
I'm adding another sump hole now, much closer to the cellar drain & with a water-powered backup. All the diagrams I've seen have the check valve up out of the hole & warn to drill a hole in the pipe to avoid air lock. Diagram-
Is there a reason that the check valve *shouldn't* go right next to the pump? It seems like that would eliminate air lock problems.
Have I just been lucky that I've never had a problem with mine set up that way? My sump pump gets a serious workout every spring and occasionally during the summer.
Jim