Corrugated plastic drainage pipe (often known as a "french drain" or "weeping tile") is a flexible pipe perforated with small holes on one side that allow water to enter the pipe from the surrounding soil. These pipes can be installed underneath a lawn to provide an easy way for water to escape during and after a rainfall. If a lawn doesn't have enough slope to drain naturally, or is made of relatively impermeable soil, installing corrugated pipe will prevent it from flooding. The installation itself is very simple.
Step 1
Mark out the path for your drainage pipe using a can of spray paint. If the area has a downward slope, follow it. Otherwise, just orient the pipe away from any nearby structures; you will be able to add a slope when you dig out the pipe trench. If you plan to drain a large area, you can mark off several trenches; they don't need to connect.
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Step 2
Dig a trench along the lines you painted. The trench should be 24 inches deep and 6 inches wide. To give the trench some downward slope, dig the far end lower than the end closest to the building. You can rent a laser level from a home improvement store to check the height and ensure that the slope is in place before you fill the trench in.
Step 3
Expose the low end of the drain pipe if possible. This can be done by having it exit through the side of a hill into a natural valley. If this isn't practical, you can simply bury the end of the pipe in an area close to a storm drain or with softer soil that will absorb more water.
Step 4
Pound the dirt at the bottom of the trench. The easiest way to do this is with a 4-by-4 post. Turn it on its end and drive it downward with as much strength as you can sustain. This will prevent soil in the trench from fouling the drainage pipe and provide a stable base that won't settle into a different slope.
Step 5
Shovel in enough 1-inch diameter washed gravel to form a 2-inch thick layer along the whole length of the trench.
Step 6
Cut your drainpipe to the length of the trench with shears and lay it down on top of the gravel layer. Ensure that the holes in the pipe are facing downwards. The pressure of the water soaking into the soil will squirt water into the pipe to be carried away. If you turn the holes upward they clog easily and will not start absorbing water until the water table rises above the top of the pipe.
Step 7
Bury the pipe in more 1-inch gravel. Keep adding it until the whole trench is filled to within 1 inch of the ground surface. This will provide an easy path for water to travel, drawing it off from the rest of the lawn.
Step 8
Hide the trench by covering the gravel with a layer of sod. If you don't mind seeing the gravel, it will drain better uncovered. You can always beautify a gravel trench by setting decorative stepping stones into the gravel along its length.
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