The Combined Drain System


  • Enjoyed your web site! It's well laid out, easy to navigate, fun to read (love the ugly photos), informative, not overly detailed, etc., etc., etc.

    My own stupid story... On my recent addition I did the back fill myself. I ran 3" perforated pipe in gravel to collect water around the foundation. The inspector said my downspouts must be piped away, so I simply connected them to that perforated pipe...guess what, my crawl space is full of water! Running downspouts into perforated pipe in gravel essentially piped all the water from my roof straight under my house. Fortunately all wood and insulation etc. is well above the "lake". I disconnected the downspouts and use splash blocks for now.

    Bob, Home owner in SF Bay Area

    Thanks for the kind words and for your story.

    There is nothing wrong with having the downspout drain line in the same trench with the foundation perimeter drain lines. But the downspout drain lines must be a "tight-line" system and at least a part of the foundation drain system must be a perforated line.

    It is also possible to join the two lines into a combined tight line once the two lines have left the area of the foundation and are below the level of all the perforated lines. The key point is to make sure that all of the roof drainage water is diverted away from the foundation. - George