odd question about plumbing

[Albertan22]

I haven't done what you're asking, but a durso does have two holes drilled in the side of the pipe. I think they're syphon breaks though, not to add more water flow. I don't know if drilling extra holes will fix your flushing problem, sounds like a backpressure issue caused by air in the line or something. How deep is your drain pipe's exit in the sump? I had a flushing problem when I first set up my system and figured out that I had my pipe exits too deep in the sump water.