What is a French Drain?

Landscape fabric lines a french drain in a yard

If water is pooling near your trees, flower or vegetable gardens, a French drain system can redirect rain or snowmelt. 

Even better? A French drain often is an easy DIY project.

And DIY will almost certainly save you on the cost of a French drain – unless you don’t do it correctly. Homeowners pay an average of $5,000 to have a French drain installed professionally, with most homeowners paying $1,650 – $12,250.

What is a Landscaping French Drain?

First, a landscaping French drain has nothing to do with France. French drains are named after their inventor, Henry French, a Massachusetts farmer, who literally wrote the book on “Farm Drainage” systems in 1859.

So what is a French drain? A French drain landscaping drainage system – you’ll need gravel, perforated pipe, landscape fabric, a shovel, and gravity – filters and redirects water to a desired runoff point. The gravel layer prevents leaves and dirt from entering into the perforated pipe, allowing the water to flow easily. 

The location, direction, and angle of your French drain are important. You’ll want to place your French drain so that it slopes. That angle enables gravity to draw water from where it’s pooling to where you want it to go.

Here’s why that pooling water can be a problem: Not only is pooling water unsightly, but it can lead to soil erosion, root rot, and damage your home’s foundation. Swampy areas are also prime breeding grounds for many pests. 

While pooling water is an obvious sign that you need to improve drainage, there are other indicators, too. One is a DIY Perk Test, which will help you decide if your soil is draining well.

How Does a French Drain Redirect Water?

Simply put, a French drain is an underground system that directs water to a runoff point, such as a retention pond, swale, body of water, or the curbside. 

Depending on regulations where you live, you might be able to direct the flow into a stormwater drain. Do not drain the water onto someone else’s property.

Because of its slight grade, a French drain has a high end, where the majority of the excess groundwater enters the pipe, and a low end where it leaves. The gravel surrounding the pipe and the perforations in the pipe allow the system to collect water throughout the entire drain field.

Gravity is what moves the water from the high point of your French drain to its low point.

A French drain collects water all along its length, as opposed to a trench which gathers water only at one spot. This allows you to control the water flow throughout all of your landscaping. 

Alternatives to a French Drain

Other ways to redirect pooling water in your yard include:

Build up the low spots: If puddles form in your yard, fill in the depression with a mound of dirt. When that settles and you have a flat surface, plant grass seed. 

Swale or valley: You’ll often find these drainage ditches alongside the road in rural areas. A swale will direct water away from your property.

Terraced slope: This is an expensive and fancy option, but imagine a terraced or sloped pathway that directs the water from a high spot to a lower spot.

Bog garden or rain garden: A puddle where plants thrive turns an eyesore into a thing of beauty.

Dry creek bed: If you live in a drought-stricken area or have a xeriscaped yard, a dry creek bed filled with rock can pool water in storms and fit in with your landscaping when dry.

You can read more about these and other options in 7 Ways to Improve Drainage in Your Yard.

Benefits of a French Drain

A French drain has several advantages in your landscaping and yard:

A dry foundation: Water gathering near your home can damage your home’s foundation. A French drain channels water away from your home, much like gutters and downspouts gather and redirect rainwater from your roof. 

A hidden drainage system: Once installed, you can cover your French drain with all sorts of gravel. A drainage ditch is an eyesore, but a French drain is underground. It works out of sight. Even better? With the right gravel or other covering, your French drain can be eye-catching.

A quick and affordable drainage solution: Installing a French drain can be a low-cost weekend DIY project. Other options above (see French Drain Alternatives) all likely will carry higher price tags – and some could be significantly higher.

4 Things to Know About French Drains

1. Digging can be dangerous: Check for electrical, gas, or water lines underground before you start digging your French drain. (This is Step 1 in How to Build a French Drain). 

2. Check if you need a permit: Some municipalities and homeowners associations may require a permit to install a French drain in your yard. Why? You might be channeling water from your yard to your neighbor’s, causing drainage issues there.

3. Slope must be 1% or more: French drains work because of gravity. Y ou need a slope or angle of 1% or greater to allow the water to work its way from the high point to the low point of your French drain. 

3. French drains can get clogged: Dirt and debris can cause your French drain to fail. Without maintenance, you could have pooling water all over again. 

FAQ About French Drains

What is the difference between a curtain drain and a French drain?

Curtain drains are built to manage surface water, whereas French drains direct groundwater. Built similarly, the primary difference is the depth. A curtain drain sits much closer to the surface. 

What kind of maintenance does my French drain need?

You want to check frequently to ensure that both the high point and low point are clear of 
obstructions. You may also need to periodically add additional gravel to the surface layer.

Can I use a catch basin and harvest the water for gardening?

Yes, you just have to set up the catchment barrel in such a way that it is below the drain’s high end. As the excess water flows through the drain, you will be able to collect water in the basin and use it for watering during dry spells.

How can you spot a French drain system?

Are you worried a French drain system would not be aesthetically pleasing on your property, but you’re not exactly sure what they look like? There are clues around your area. You just have to know what to look for.  

French drain systems are quite common and can vary in size depending on the amount of runoff to be captured and redirected. They are in business campuses, new construction sites (you’ll see catch basins), playgrounds, and maybe on some of your neighbors’ properties. 

To identify a French drain system, look for a riverstone (rocks) drainage ditch and a drain box hidden under rocks or stones. The stones would be large enough not to get washed away, and the drain box collects the water runoff, indicating the entry point. 

Also, look for a “daylighted pipe” at the end of the system — a small segment portion of pipe that’s not buried, but exposed to daylight, shows where the water empties out. The exit point could flow into a municipal storm drain, onto a lawn area farther away from a building/house, or into a catchment basin.  

When to Hire a Pro to Install Your French Drain

French drains are a pretty easy DIY project, if you don’t mind getting your hands dirty. You’ll most likely need a day or two and a friend or two to help dig the drainage area and place the gravel, pipe, and landscape fabric.

If that sounds like too much work or you’d rather spend your time doing something else, hire a landscaping pro near you who’s experienced at putting in French drains in yards. 

There’s also the chance that you might not do something right in installing your French drain. Hiring a pro saves you from making a potentially costly mistake going the DIY route with your French drain. 

LawnStarter writer Harley Grandone contributed to this report.

Main Photo Credit: Shutterstock with text overlay

Alison Hoover

Alison Hoover

Alison is a Midwesterner through and through, and loves to spend her time baking and reading. Always at home in the dirt, as a kid, Alison raised a vegetable garden with her dad, and flower gardens with her mom.