Lawn and Garden

Installing a French Drain

Lawn + Garden Projects

Installing a French Drain

  • Skill Level: Beginner
  • Estimated time: 3-4 hours (varies depending on size)
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BLACK+DECKER B+D Contributor 193 Projects

A French drain is a very simple, but very effective solution for poorly draining lawn areas. It involves digging a trench for gravel-covered length of pipe that filters runoff from the lawn, leading it to a low-lying area such as a gutter or wooded section of the property. Never direct a French drain or any other drainage improvement to a neighbor’s property.

The most important part of the French drain is the slope. Maintaining a reasonable slope ensures that the runoff will follow the drain. The drain tube itself is covered with permeable landscape fabric. The idea is to allow for water to flow through, while blocking fine soil that could clog up the holes in the drainpipe. Do not use rubber or standard plastic sheeting or pond liners. These will not allow for the free flow of water. You should use clear gravel to surround the pipe for the same reason. Don’t use gravel with fines that could clog or block the holes in the drainpipe.

Your tile should underlie the lowest part of the problem area and slope slightly toward an above-grade exit point. Use a 2 x 4 with a level on top to ensure the trench floor carries a gentle downward slope. The trench needs to be at least 1 inch deep where gravel covers it in the problem area. The tile will exit into the gently sloped swale that will carry the water away.

How to Install a French Drain

  1. Installing_French_Drain_01

    Use stakes, mason’s string, and a string level to determine a drain path with an above-grade exit point below the level. Use a power edger or spade to cut the turf at the outside edges of the drain trench—usually 8" to 14" wide.

  2. Installing_French_Drain_02

    Use a handheld turf cutter or spade to dig up the sod along the trench line. Store the cut sod in a cool, shaded place and moisten regularly while you dig the trench.



  3. Installing_French_Drain_03

    Dig out a squared trench over the length of the drain. Place the dirt on a tarp next to the trench site. Use a 2 x 4 with a level on top to ensure the trench slopes slightly to outlet.

  4. Installing_French_Drain_04

    Line the bottom of the trench from start to end with permeable landscape fabric wide enough to run 1 ft. up each side. Add about 1" of washed gravel to the bottom of the trench.


  5. Installing_French_Drain_05

    Lay perforated pipe (called drain tile) all the way along the trench. Gravel is not needed toward the exit of the tile where the trench becomes shallow.

  6. Installing_French_Drain_07

    Add 3" to 4" of gravel on top of the pipe and then fold the edges of the landscape fabric over the top of the gravel and pipe, essentially making an outer sheath of fabric. 

  7. Installing_French_Drain_06

    Fill the trench with soil, and tamp down, leaving about 1" for the sod. Scratch the top of the soil lightly with a garden rake.

  8. Installing_French_Drain_08

    Replace the sod you removed. Roll the sod to ensure firm contact with the soil and water well along the length of the trench. Cover the outlet of the tile with a PVC grate and/or large rocks.

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What You'll Need

Tools

Black and Decker - 20V MAX Lithium 12 in High Performance TrimmerEdger - LST400 20V MAX* Lithium 12 in. High Performance Trimmer/Edger Black and Decker - Full Wraparound Eyewear with Rubber Temple Grips - BD250 Full Wraparound Eyewear with Rubber Temple Grips Black and Decker - ACCUMARK 36 in Level - BDSL10 ACCU-MARK™ 36 in. Level