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Our house—built in 1989 in the Kansas City, MO area—has a walk-out basement with exterior foundation drain pipes daylighted. The drain pipe on the east wall had a complete blockage, so I dug it up in order to replace it. The drain pipe—4-in perforated, corrugated black pipe—was sitting on top of the footer. What is the proper location for the drain pipe—on the footer or next to the footer? Or to be safe, should I install one drain pipe on top of the footer and another next to the footer?

East Wall Excavated to Footer

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You can install your drainpipe on your footing or next to it, but the critical issue is that it is BELOW your basement slab.

Drainpipe systems are designed to capture ground water leaking down from storm water, downspouts, etc. AND from a rising watertable.

Ideally the 4” perf pipe should be encased in about 12” to 18” envelope of drainrock and protected with a filter fabric wrapped around the drainrock envelope. (This fabric will keep the soil from flowing int the perf pipe and plugging it again.) In addition the basement wall should have a waterproofing (mastic) applied to it and then cover the mastic with a mesh that protects the mastic when you backfill and allows water to “flow” down the surface of the wall and directly into the perf pipe. (Make sure the mesh extends into the drainrock envelope.)

We like the bottom of the perf pipe to be about 4”-6” below the bottom of the basement slab.

You say your pipe daylights, which is good. Make sure it flows down and do not tie downspouts into it, because it could overflow the system and backup to your basement wall.

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From the research I've done, the Green Building Advisor Q&A on this topic and resultant article by Scott Gibson titled "How to Install a Foundation Drain" provide good reasons for either placing the drain pipe on or next to the footer. Some of the key points include:

  • James Morgan's primary reason for placing the drain pipe on the footer is that "the seam between the footing and the foundation wall is a vulnerable location but it takes actual hydrostatic pressure to push moisture through it."
  • Martin Holladay discusses accounting for groundwater and prefers to "install the footing drain around the entire perimeter of the footing, equal in elevation to the bottom of the footing or only slightly higher (to make room for a thin layer of crushed stone under the pipe), installed dead level. The installer makes a burrito with landscape fabric (geotextile fabric), so that the pipe is surrounded by crushed stone and wrapped up to prevent fines from clogging the holes. The holes are placed at 4 o'clock and 8 o'clock."
  • No matter where the drain pipe is placed, the center of the drain pipe needs to be below the top of the concrete slab floor inside the basement.
  • Steve Knapp—the original poster of the Green Building question on this topic—decided to do both.

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