A French drain also called weeping tile or channeled drain is a channel filled with stone or other solid materials or containing a perforated drain that directs groundwater away from a cavity. The water then flows into a drain hole of the same type, emptying into a sewer system or directly into a storm drain system. They can be constructed using various materials including clay, cast iron, sheet metal, wood, fiberglass, stone, concrete, plastics, mosaics, marble, and ceramic. It is sometimes necessary to install a specialized French drain in an area prone to foot traffic such as a sidewalk or street.
The installation of a French drain is usually a single pass, one or two-piece unit connected to a post hole in the earth. The material used in the application of the drain includes French drains made of clay, cast iron, sheet metal, wood, fiberglass, concrete, plastic, and ceramic. In urban areas, French drains made of concrete and asphalt are used for larger parking garages. The size of the pipe is dependent on the amount of water that collects in the pipe.
There are a number of causes of a French drain becoming clogged. Most often, the problem is caused by a previous installation, such as a French drain connected to a baseboard or floor drain in a basement. In this scenario, dirt or hair picks up the water as it percolates through the home, then drops down onto the French drain. Over time, the dirt and debris collect on the inside of the pipe, forcing it to become clogged. Clogging is most often a problem when rainwater is directed onto the French drain system, which can happen when a sump pump is in use or when the French drain is connected to a sump pit.
Improper excavation around a French drain can cause soil to percolate inside of the pipe, slowing its flow. If the French drain is connected to a garden hose, this soil pressure can be alleviated by placing landscape fabric along the base of the French drain trench. When dirt and debris collect on the inside of the French drain, it becomes a physical barrier that slows the water’s flow through the system. A French drain that is not connected to a garden hose or another type of external source of water can become completely clogged if this happens.
As mentioned earlier, French drains are connected to basement floors via a trench with a two-foot-deep opening. It is possible to install French drains that are wider than two feet deep. This can allow for the connection of two French drains, providing an extra outlet for runoff water. However, French drains that are too wide will also create a layer of soil on the interior of the trench that will slow down the water flowing through the French drain system.
There are a number of ways to solve problems with French drains. One of these methods involves excavating an appropriate distance from the French drain to the exterior of the house. After excavating this space, add a foot of earth at the bottom and fill it with gravel. The excavated area should be between three and four feet deep. Once the gravel is in place, the French drain can be placed inside of the three-foot-deep excavated area.
If the gravel does not hold water well, then a sloped driveway could be installed instead. If the gravel does not slope properly, then a layer of wood shavings could be added to the bottom of the French drain to help the soil in the excavated area slope more. Wood shavings tend to keep soil down better than large pieces of dirt. Also, planting grass can help keep water away from the roots of the grass, which could cause roots to grow up through the French drain.
Another way to remove excess water from French drains is to install French drains that attach to the edge of the yard. These are usually made of galvanized steel. These trench drains can run as low as one foot of water, and they are much easier to install. Some of these trench drains can also be installed underground if the French drain is attached to the side of the property. These drains will be connected to a sewer line. They are often the best solution for older homes that may have clay foundations.