I have a 90 year old house that is located on a flat lot. To drain water from my crawl space I have trenched around the inside of the crawl space. Since my house lot is flat and sectioned off where it was added to over the years, I had to install 3 sump pumps located around my trench. I have installed tarp, and a de humidifier and things are dry most of the time.

My problem: On one side of my house the trench is obstructed by my cast iron sewer line exiting the house. It cause the trench not to flow down to my sump pump. I do not want to raise the level of the trench above the sewer line. Adding another sump pump would correct this but cost $300 and a days work for me.

Would a two foot section of water hose or PVC pipe going underneath sewer line work? The water would flow down in the hose but would have to rise up several inches after the sewer line to regain the trench on other side.

Any ideas?

  • I don't think there's any way to make water flow upward without a pump. If the soil drains poorly on the other side of the sewer line then some of the water might rise enough to make it into the trench, but not all of it. And if it drains well then probably none of it will make it. Apr 20, 2015 at 18:38
  • It would still be about a days work but why not lower the trench and the sump pit? If you're sewer drain is "floating" for a few inches it should be okay or you could brace it to be sure.
    – Dano0430
    Apr 20, 2015 at 20:06

1 Answer 1


If the exit of the proposed pipe is lower than the entrance, this will work fine, but it will leave standing water in the pipe itself below the exit. If the exit is the same level or higher than the entrance, this will not work and you will need a pump.

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