An exterior French drain usually consists of a trench, often lined with landscaping textiles that prevent clogging from dirt or roots, as well as reducing the possibility of the drainage material from migrating, one or two perforated pipes surrounded by gravel, (depending upon sizing and redundancy requirements and always placed perforated side down), and covered with sand for further filtration of sediment. The advantages of an exterior French drain system are:
- Relatively low cost and easy installation
- Generally low maintenance (a French drain can last up to ten years without maintenance)
- It can be covered inconspicuously with turf to maintain the aesthetic beauty of the landscape.
In addition to their primary function of directing water away from your home, exterior French drains are also environmentally proactive as they can lead to a dry well, a structure that returns excess water to the supply of groundwater, or to a rain garden, an environmentally friendly invention that uses wetland plants to absorb excess water and return it to the atmosphere through transpiration.