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

  • Hello, and welcome to Home Improvement. It's hard to tell; would you add another picture or two? Apr 18, 2019 at 22:45
  • I think the leak was cause when I added the backup pump and the pipe into the foundation angled slightly downward, allowing water to run back on the underside of the pipe. I can raise the pump a bit to adjust the angle. But I'd like to fix it so that water can't just drip back into the house if the pump ever gets knocked. Since the 3" pipe is flush with the foundation, I can't add a reducer to connect the pipe properly.
    – perogiex
    Apr 22, 2019 at 12:25

1 Answer 1


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.

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