How to Install a French Drain Trench


French drain trenches are used to direct runoff away from buildings and to drain standing water into an area where it can't do any harm. Installing a French drain trench is straightforward, but it does require physical labor. You can simplify the process by renting a Bobcat or small backhoe from a tool rental store.

Things You'll Need

  • String lines
  • Shovel, backhoe or Bobcat
  • Gravel
  • Perforated pipe
  • Pipe joiners
  • Filter fabric
  • Topsoil
  • Sod
  • Determine where you will build the French drain. A trench for diverting water from a house should be at least 6 feet long and perpendicular to the foundation, and it should not end in an area that could become swampy. Placing a drain on a downward slope is ideal, but if you don't have a slope, make the end of the trench deeper.

  • Use two string lines to mark the sides of the trench. They should be 3 feet apart and parallel to each other.

  • Dig a trench between the string lines that is at least 2 feet deep. Flatten the bottom of the trench, then add a 2-inch layer of gravel. Smooth out the gravel.

  • Lay a length of 6-inch perforated pipe in the trench. If you need to add length, join pieces of pipe together with pipe joiners. Cover the pipe with another layer of gravel and add a layer of filter fabric on top of the gravel to help keep the pipe from clogging.

  • Add topsoil to the trench so that it is level with the rest of the landscape. Tamp the topsoil down and lay sod or other landscaping materials. Don't pave over the French drain.

Tips & Warnings

  • Build a simple French drain by filling a trench with river rocks or gravel. Eliminate the pipe and add enough gravel and rocks to reach ground level.
  • A French drain that becomes clogged will need to be excavated and redone.

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  • Photo Credit Raftertales
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