Step-by-step how to install a French drain on laterite soil

A French drain is a highly effective subsurface drainage system to solve waterlogging problems in laterite soil. Here’s a step-by-step guide to installing one:

1. Plan the Route: Identify the center of the waterlogged area. Plan a trench that runs through this area and slopes gently downhill (a drop of about 1 foot for every 100 feet of length) towards a safe water outlet, like a ditch or a non-cultivated lower area.
2. Dig the Trench: Dig a trench along your planned route. A standard size is about 1 foot wide and 1.5 to 2 feet deep. Ensure the bottom of the trench is smooth and maintains a consistent downward slope.
3. Line the Trench with Geotextile Fabric: Roll out a water-permeable geotextile fabric (also known as landscaping fabric) and line the bottom and sides of the trench. Leave plenty of extra fabric on both sides to fold over the top later. This fabric is crucial as it prevents soil and silt from clogging the drain.
4. Add a Gravel Base: Pour a 2-inch layer of clean, coarse gravel (1 to 2 inches in diameter) at the bottom of the fabric-lined trench.
5. Place the Perforated Pipe: Lay a 4-inch diameter perforated drain pipe on top of the gravel. Make sure the holes in the pipe are facing downwards. This allows water to enter the pipe from the bottom as it rises in the trench.
6. Cover with Gravel: Fill the trench with more coarse gravel, covering the pipe completely and leaving about 4-6 inches of space from the top.
7. Enclose the System: Fold the excess geotextile fabric over the top of the gravel layer. This completely wraps the pipe and gravel, protecting the entire system from soil intrusion.
8. Backfill the Trench: Finish by filling the remaining space with a layer of coarse sand and then the original topsoil. You can then plant grass or shallow-rooted plants over it.