How Effective Is a French Drain?

French drains are perforated pipes laid in a gravel bed, usually intended to shunt water away from house foundations.

The French Drain

French drains divert rainwater away from foundations or flood-prone garden areas.French drains divert rainwater away from foundations or flood-prone garden areas.
When properly installed, French drains can be effective methods for foundation protection and water diversion. A properly directed French drain has the added benefit of supplying water for your landscaping or water catchment systems.

French drains involve, at minimum, a trench filled with gravel, designed to collect rainwater and carry it away from problem areas. French drains can also include a perforated pipe sunk into the gravel to more quickly and efficiently collect and divert water. French drains can be installed in a garden space or inside or outside the foundation of a building. Internal french drains will usually require a holding tank and the installation of a sump pump to carry away the collected water.

History

The general misconception is that the French drain actually hails from France. The French drain invokes bucolic images of water dripping from the eaves of country cottages and an ancient history of water-diverting practices along driplines.

It is possible that such a technology cropped up in the French countryside. However, the French drain as we know it was actually developed by American judge and farmer Henry French of Concord, Massachusetts. The design was first published in a book by French in 1859, titled "Farm Drainage"

Effectiveness

When properly installed, French drains can be a very effective means of water control. The systems are entirely buried and protected by rock, and so rarely if ever back up due to debris. Systems built without a sump pump require little to no energy input. With minimal parts to break, clog, or back up, the system is generally efficient and low-maintenance.

The effectiveness of a French drain depends on its design and implementation. Take into account your needs and desires, as well as the topography and landscaping in the area, before designing your French drain. Consider having your French drain professionally installed for maximum effectiveness, especially if you decide on an internal French drain, installed inside the footprint of your home.

Problems

The landscaper must understand potential issues with French drains before, during, and after construction in order to build an effective long-term drainage solution for the area. Two major concerns are erosion at the outlet point and termite attraction.

Over time, the collected and redirected water, which will move more quickly and efficiently in a pipe, can cause erosion at the outlet point. Landscape the outlet area with hardy plants that can be used for erosion control, and direct the system in such a way that the natural topography will disperse the water across a wide area rather than creating a trench. Or turn a problem into a plus: consider designing a water catchment system such as a cistern, and reuse potential floodwaters to water your garden.

French drains, with moist conditions and enclosed nature, can also attract termites and exacerbate existing termite problems. Consult an exterminator before constructing a French drain along the edges of a building foundation, and you may save yourself a headache down the line.

If you plan, design, and implement your French drain well, you can avoid problems and maximize the drain's potential. Under these conditions, you will create an effective, low-maintenance, and long-lasting solution to your drainage or flooding problems.

About the Author

Ellie Maclin is freelance writer with more than 10 years of experience. She contributes to online and print publications, specializing in topics such as historical places, archaeology and sustainable living. Maclin holds an M.S. in archaeological resource management from the University of Georgia, as well as a B.A. with honors in anthropology from the University of North Carolina.