Plumbing – Fixing sump pump discharge

leakplumbingsump-pump

Could someone explain exactly why this discharge system works or what I need to do to fix it? I installed a backup sump pump last month. I noticed that the discharge pipe going through the wall was loose. Like really loose, like it wasn't even attached to anything on the other side of the wall. The pump was turning on once or twice an hour all month while it dealt with the spring thaw. But yesterday, a puddle of water appeard on the floor. I pulled apart the wall and saw water dripping behind the vapour barrier through the insulation. When I moved the insualtion I saw the pictured setup with the pipe sitting loose inside a much bigger pipe. I pushed the pipe in further and there hasn't been any more leaking. It looked like the bottom gap between the two pipes may have been taped at some point.

Before I seal up the wall, what should I do with this discharge pipe? Should I seal around it with expanding foam? How has my basement stayed dry all these years?
Picture of discharge pipe through the foundation

Edit: Adding more pictures. You can see the large PVC pipe stuffed with insulation.
close up of discharge into foundation
sump pump overview

Best Answer

Since the 3" pipe is flush with the foundation, I can't add a reducer to connect the pipe properly.

Chisel out a half an inch around it so you can get a rubber repair reducing coupling on there.