What Is A French Drain? How to Install a French Drain

A French drain is a water drainage system made from a gravel-lined ditch with a length of pipe that routes water away from a building’s foundation. French drains are used to manage groundwater, stormwater, and drainage problems. The French drain system prevents excess water from building up after heavy rain in areas where it can do damage to building foundations, basements, retaining walls, or landscaping and hardscaping areas.

A French drain allows proper drainage of excess surface water collecting on the ground to somewhere that it can properly drain into. Here is an overview of how the process works.

1. 1. The ditch collects water. A French drain always involves a sloped ditch that excess surface water can run into.
2. 2. The gravel prevents erosion. The ditch for your French drain is lined with a layer of landscape fabric and gravel, which prevents the runoff from eroding your soil.
3. 3. The pipe reroutes the water away from your building foundation. A solid or perforated pipe protected by landscape fabric and gravel will run the length of your trench. If you have a perforated pipe, the water can seep inside as it travels down your trench. If you have a solid pipe, it will drain through the mouth of the pipe at the bottom of the trench. Your water can be routed to a municipal storm drain.

French drains are effective ways to prevent too much moisture from creating damaging water pools or seeping into your foundation and causing problems. Here are some of the potential benefits of the french drain system.

1. 1. They’re effective as waterproofing your foundation. A French drain system is very effective at waterproofing your home's foundation and keeping excess water away from your home.
2. 2. They’re inexpensive. The materials and installation for French drains are cheap and easy to execute, making them an effective option for waterproofing your home.
3. 3. They can last a long time. Once you’ve installed your French drainpipe, it can last for decades with minimal upkeep and maintenance.
4. 4. They’re easy to clean. Problems with your French drain like clogging or drainage issues can be simply cleared up by flushing water down the pipe until the normal flow of water resumes.

A French drain may not be suitable for every home. Some of the potential drawbacks to having a French drain include the following.

1. 1. They can disturb existing landscaping. Installing a French drain requires you to dig a sizable trench on your property. The trench can interfere with the root systems of already-established landscaping, and some property types—like homes with HOAs—may not allow you to dig a trench.
2. 2. They can be labor-intensive to install. Digging the deep trench and installing your French drain can be labor-intensive, and homeowners may want to consider hiring a professional installer.
3. 3. They can leave you with excess dirt. When you install a French drain, you don’t back-fill the trench hole with the soil you dug to make it. This means that you will likely be left with a sizable pile of dirt. Make a plan to dispose of your excess dirt after you dig your ditch.

Though French drain installation requires some work, time, and strength, you can easily do it in your own yard. Follow these step-by-step instructions to install a French drain in your own yard.

1. 1. Dig a trench in your yard. The first step is to dig a trench from the area where the most water builds up in your yard to where you want it to go. The trench should be sloped down towards the lowest point, with a slope of one-inch depth for every one foot of length. Make your trench at least a foot wide. The wider your trench, the more effective your French drain will be. If you want to make a trench near your home to prevent foundation or basement damage, make sure that the trench is below the slab level.
2. 2. Prepare the trench. Cover the bottom of the trench in gravel or crushed stones. Cover the gravel in a cut piece of filter fabric to ward off weeds.
3. 3. Lay your drainage pipe. Lay your drainage pipe along the length of the trench. You can use either PVC pipe or flexible plumbing pipe. With PVC pipe, drill holes into the bottom side of the pipe for water to enter through. PVC pipe is easy to clean, but flexible pipe is easier to work with and position.
4. 4. Cover the pipe. Wrap your pipe in a water-permeable landscaping fabric to protect it from roots and dirt. Then cover the pipe by filling the trench with the remaining gravel or crushed stones. You can also add a layer of topsoil to the top of the trench, but this will make maintenance more difficult if you need to check the pipe.

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