What is a French Drain?

Niki Foster

A French drain is basically a ditch lined with rocks or gravel that helps drain water away from an area. It is generally used in gardening or to protect the foundation of a house or other structure from ground and surface water. One may also be used as backup for retaining walls or to drain water away from a septic tank.

Gravel may be used to line a french drain.
Gravel may be used to line a french drain.

This type of drain works on the principle of gravity, being slightly sloped down from the area to be drained to the area where a homeowner wishes to redirect the water. It is typically lined with perforated clay pipe and surrounded with a landscaping textile to prevent dirt or plant roots from clogging the system. Excess ground and surface water percolates into the drain and is directed away.

An early version of what is now known as the French drain was used in ancient Rome.
An early version of what is now known as the French drain was used in ancient Rome.

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The French drain is named after Henry French, a judge and farmer, and discussed in his 1859 book on the subject, Farm Drainage. The design predates French by many centuries, however, as a version was used in ancient Rome. The system continues to be one of the most efficient and widely used methods of redirecting water, though it has been improved upon over the years.

A French drain is a ditch that helps to drain water from an area.
A French drain is a ditch that helps to drain water from an area.

Modern drains are often installed well underground and hidden from view, and they may be covered with sod. A French drain 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.

Most gardeners or homeowners can build a French drain relatively easily, but many countries, including the United States and the United Kingdom, regulate the use of these drain systems to keep certain contaminants out of the water supply. Anyone considering installing one should consider the relevant city codes and effects on their neighbors' property.

A French drain can be used to drain water away from a septic tank.
A French drain can be used to drain water away from a septic tank.

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Discussion Comments

LittleMan

Is there a particular type of pipe that works well for a French drain? Pipes never really concerned me until I learned that the basement in my new house is actually a swamp when it rains, and I'm going to have to install a French drain near the basement along with a sump pit.

So, in my French drain/sump pit endeavor, what kind of piping should I use? PVC, copper, other kinds? I am really kind of at a loss because I've never had to do anything like this before, so I'd appreciate all the input I can get! Thanks guys!

EarlyForest

Is it possible to top a French drain design with gravel, or do I need to do it more like a French drain tile type of construction?

I want to put a few French drains in my yard, so I'm looking over designs and construction and things like that. So what would you say? French drains with gravel, or French drains with big rocks, or French drain in a drain tile style?

Charlie89

I always wondered what those things were called. A neighbor of mine is big into gardening and has french drains that slope all the way down into the creek that runs behind both our houses.

I never paid a whole lot of attention to them, I just thought she liked the way the rocks looked or something. Now I know they actually have a practical purpose. Who knew?

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