How to Correct Drainage in a Backyard
Poorly drained backyards cause pools of standing water on your lawn that weaken plant roots, serve as breeding grounds for disease-spreading organisms and weaken the foundation of a nearby building after a heavy rain. Most drainage problems are caused by clay soils or improperly sloped yards. Installing a French drain, or a linear series of underground pipes, directs water from a poorly drained part of the backyard to a predetermined outlet point, preventing it from accumulating and pooling around grass or plants. Does this Spark an idea?
Things You'll Need
- Graph paper
- Powdered chalk
- Measuring tape
- Shovel
- Hand tamper
- Crushed rock
- Perforated pipes, 4 inches wide
- Agricultural fabric
- Gravel
Instructions
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1
Sketch your backyard on graph paper to determine the route the French drain will take. Include the locations of paths, walkways, trees and plants so you work around them. Also, include the exact locations of underground utility lines after marking them on the ground with powdered chalk.
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2
Draw a straight dotted line on the sketch to determine the route for the pipes, starting from the poorly drained part of the backyard to the area where you want the excess water to flow out into, which is usually an area with natural vegetation.
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3
Spread powdered chalk on the ground in your backyard to mark the route the French drain will take. Refer to the detailed sketch for the exact placement of the drainage system. Measure the length from one point to the other to estimate how much piping you need.
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4
Dig a trench that is 10 to 12 inches deep and 5 to 6 inches wide over the chalk marks. Because the drainage system relies on gravity to transfer water, slope the trench by 1/4 inch per foot to assist excess water flow away from your house or plants in the backyard.
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Tamp the excavation with a hand tamper to firm the soil. Spread a 2-inch-thick layer of crushed rock over the compacted soil at the base.
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6
Lower agricultural fabric over the crushed rock. Extend excess fabric along the sides upward and outward over the walls of the trench. Overlap adjacent fabric by several inches, using as many as necessary to cover the trench.
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7
Lay perforated pipes lengthwise into the trench, with the drainage holes pointing down. To join adjacent pipes, insert the fluted end of one into the straight end of the other until they fit securely. Extend the end pipe at the outlet point by 4 to 5 inches to channel the flow of excess water.
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8
Cover the top of the pipes with excess agricultural fabric you extended over the walls of the trench.
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9
Pour gravel into the trench, directly above the perforated pipe, to within 4 inches from the edge. Spread soil to fill the remaining gap in the trench, until level with the surrounding area. Tamp the soil with the back of your shovel to firm it.
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Tips & Warnings
Consult with your local building codes office for any permits you may be required to obtain.
Always purchase 5 to 10 percent more piping than required to be sure you have enough.
Plant grass seed or lay sod over the exposed soil covering the drainage pipe so it blends with the surrounding area in the backyard.
