What is this strange plumbing on my sump pump drain?
&quot;Professionals&quot; can be idiots too. That serves no purpose and, accordingly, has no code requirement. You can cut it out, move it and all you need to do is ensure you have a check valve near the exit from the sump pump and a long 90 (avoid a hard 90 with a drop like this) to the entrance to the lateral. You should install a clean-out near the exit from the building as well, i can't tell if it's there or not. Make sure all joints are properly glued, and the clean-out threads are taped, when done right you'll be protected from any potential back flow.
I'm certain this was done after the initial install. My guess is that a previous homeowner remodeled the original work with the idea of some kind of a water hammer arrestor or perhaps they had some backflow and didn't know how to actually prevent it... is there a check valve on it now?
I can tell from the various parts, like the different-colored/cheapo-corner-hardware-store wyes, the coupling above the lower wye, the flexed upwards pipe before the upside down trap, and the not to code opposing 90s at the entrance to the lateral, that whoever installed this had no idea what they were doing but apparently had some money to throw away on a little m.c. escher inspired plumbing project. I highly doubt this is original work or the work of a plumbing journeyman... unless they were tripping.
Rip it out, run it straight, level, plumb, and include the components noted above.
You do not need a backflow preventer as long as the joints are correctly sealed, the pipe runs above the level of the highest point in the system serving your area, and there is no reason to suspect backflow forces in excess of the joint strength. For the uninitiated