How to Install a French Drain

French drain covered in small rock

If your lawn looks like a lake after it rains, you need a drainage solution. Standing water can harm your grass and home’s foundation. It can also become a breeding ground for pests, but a French drain is a simple solution to your water worries. This guide will show you how to install a French drain yourself step-by-step.

What is a French drain? 

A French drain might sound like it belongs in the Palace of Versailles, but it’s nothing fancy. It’s essentially a dressed-up trench that uses a mild slope to carry water from one place to another. The water filters from the surface, enters the drainage pipe through small holes, is carried underground, and is deposited at an exit point.

A French drain comprises a few common components:

  • 18-inch deep trench
  • Perforated pipe
  • Landscaping fabric
  • Gravel

Now that you have the big picture, let’s dig into the details of French drain installation.

How to install a French drain in 7 steps 

Man clears mud from drainage ditch in driveway

1. Gather the materials

Before you can start the installation, you need supplies. Here’s everything you need for this DIY project:

  • Drain pipe
  • Pipe connectors (if you need more than 100 feet of pipe)
  • Drill (if your pipes don’t come with holes)
  • Level
  • Landscape or filter fabric
  • Gravel
  • Shovel, trencher, or mini excavator
  • Spray paint, flags, or stakes

You can find all these supplies at your local home improvement store. They also offer equipment rentals. 

2. Choose your endpoints

Most homeowners can see the problem area–every time it rains, their yard turns into a swamp (note: if your yard becomes swampy when it’s not raining, it could be a broken pipe rather than drainage issues). This excess water is especially dangerous if it’s near your home’s foundation. Your French drain should begin where the water pools.

You might know where you don’t want water, but what about where you do? Choosing an exit point for your French drain is an important step. Do you want to collect the water for later use or filter out contaminants before it reaches the waterways? 

There are a few different options for exit points depending on your interest:

  • Municipal storm drain: This is a public drainage facility, like a curbside storm drain. 
  • Dry well: A dry well moves surface water underground. It’s just what it sounds like–a well with no water. 
  • Rain barrel: A rain barrel collects stormwater for use on lawns and gardens. You can buy one from a home and garden center or sometimes from your local government. You’ll need to connect a sump pump to the end of your French drain system to propel the water into the barrel.
  • Rain garden: A rain garden is planted in a water collection area, such as a depression in your landscape. They feature plants that don’t mind soggy soil. The plants’ roots filter chemicals out of the water as it sinks into the soil. Connecting your French drain to a rain garden only works if your area has medium to low annual rainfall (a rain garden isn’t enough to handle heavy water runoff).

Pro tip: Once you know the French drain’s start and end point, mark the path with spray paint, flags, or stakes.

3. Dig the trench

Important safety tip: Before you get started digging your trench, put down the shovel and pick up the phone. Ring the call-before-you-dig hotline at 811 to get information from your city about where underground utility lines are located. Once you know your plan for the trench won’t include any shocking surprises, you can get to digging. 

Digging your trench will go much faster if you enlist the help of your friends. Remember that time you helped your friend carry that sofa to their new place? This is the time to call in the favor.

For French drains, the trench should be at least 18 inches deep at the shallowest point and 9 to 12 inches wide. For gravity to carry the water to the desired exit point, there needs to be a slope of at least 1%, or about a 1-inch drop per 8 horizontal feet. Every 8 feet, insert a stake 1 inch lower than the previous one. This will be your guide. Use a level to check your work.

Digging tips:

  • Lay a tarp along the sides of the trench so you can easily move the soil after you’re done. 
  • Keep equipment away from the sides of the trench. 
  • Don’t stress the slope too much–you can easily move the gravel to adjust the slope of the pipe later on. 
  • Rent a sod cutter to make grass removal quick and easy–it also will preserve the grass so you can add it back later.

4. Line the trench with landscape fabric

Landscape fabric (also called geotextile fabric) keeps soil and plant roots out of your French drain. Because it uses a perforated pipe, it’s at risk of being clogged by adventurous plant tendrils, which could ruin all your hard work. 

There are two main types of landscape fabric: woven and nonwoven. For French drains, look for a nonwoven fabric. Water flows easily through this type. Choose a medium-weight fabric (4-6 ounces). Textiles in this category are great for controlling erosion and facilitating drainage. 

Pro tip: Look for products labeled drainage or filter fabric. That way, you can avoid non-permeable fabrics and guarantee the water can pass through.

Installing the landscape fabric is straightforward. Lay enough landscape fabric to cover the bottom and sides of the trench. Leave about 10 inches of fabric on each side so you can fold it over the pipe and gravel later. You can use landscape fabric staples to secure it in place as you’re laying the gravel.

5. Fill with gravel

A man Digging ground to prepare for drainage home.

Your next step is easy: Pour a layer of gravel on top of the landscape fabric. Gravel allows water to filter through and improves drainage. Your layer should be around 3 inches deep

What kind of gravel should you use for a French drain? 

Avoid pea gravel and crushed rock and opt for round, washed rock ½ to 1 inch across. You don’t want the gravel to clog your pipe or impede the flow of water. 

How much gravel do you need for a French drain?

Gravel is usually available in cubic feet. To figure out how many cubic feet you’ll need for your French drain, multiply the length by the width by the depth. 

For French drains, the depth will be 3 inches, which is 0.25 feet. For example, if your French drain will be 30 feet long and 1 foot wide, you would use:

30 x 1 x 0.25 = 7.5 cubic feet 

If you’re looking at gravel that comes in pounds, you’ll need an additional step. 1 cubic foot of gravel is equal to about 96 pounds, so you’ll multiply your cubic feet by 96 to figure out how many pounds you need. For the example above:

7.5 x 96 = 720 lb of gravel 

6. Add the pipe 

After all that prep for your French drain, it’s finally time to install the pipe. Choose a perforated pipe to prevent a messy spout at the exit point. 

The actual installation is easy. All you need to do is lay the pipe on top of the gravel bedding with the holes facing the ground to reduce the risk of the top layer of stone and soil causing clogs. Some pipes have holes on all sides to allow more water in. 

What kind of pipe should you use for a French drain? 

Look for a 4-inch diameter pipe. Any smaller and you risk clogs. Many homeowners choose corrugated pipes for flexibility and affordability, but rigid PVC drain pipes have superior durability and crush resistance. You can buy these pre-perforated or drill holes in a zigzag fashion every 2 inches.

7. Cover the pipe

Once you lay the pipe, cover it with a few more inches of gravel. Next, wrap it with the excess fabric like a burrito. These layers protect the pipe from any dirt and plant roots on top of your French drain. Fill in the rest of the trench with topsoil, sand, or gravel.

8. Add finishing touches

Looking into a French drain covered in rock

After the pipe is installed, it’s time to beautify your French drain so it blends seamlessly into your landscape. You have a few coverage options. You can use crushed rock and leave it at that, or you can add larger rocks of different shapes and sizes for a look akin to a dry stream. 

If you want an even more blended look, cover with about a 3-inch layer of gravel, then a layer of landscape fabric, and finally a layer of topsoil. Add ground cover plants to conceal your new drainage system in green. If you cut a section of your sod and removed it to dig the trench, you can cover the area with that sod or reseed it. 

FAQ about installing a French drain

What are the benefits of a French drain?

A French drain has a relatively quick installation process compared to other systems. Other benefits of French drains include getting rid of standing water, controlling erosion, and minimizing toxic rainwater runoff.

How long does French drain installation take?

Professional installation can take as little as 6 hours. If you’re doing it yourself, expect to spend the whole weekend. 

How much does DIY French drain installation cost?

In total, DIY French drain installation costs around $528 for a 25-foot drainage system, including trencher rental, tools, and supplies. That comes out to around $21.12 per linear foot.

Here’s how that cost breaks down:

DIY equipmentAverage cost
Renting a sod cutter for a day (or use a shovel)$110
Tape measure$10
Marking flags — 100 pieces (or use spray paint or stakes)$13.50
Trencher rental for 4 hours$60
Level (to measure pipe angle)$20
Wheelbarrow (to carry dirt after digging)$140
4 to 6 oz. non-woven drainage landscape fabric$59
1 ½ cubic feet of pea gravel$38
4-inch PVC pipe$30
Catch basin$47
Total DIY cost (project size: 25 feet long, 10 inches wide, 18 inches deep)$528 or $21.12 per linear foot

The average cost of professional French drain installation is between $10 to $75 per linear foot. While many homeowners save money with DIY installation, professional installation can be cheaper in some cases. You may find the extra cost of professional work worth your while due to expertise and time saved.

How do you maintain a French drain?

Regular maintenance is key to prolonging the life of your new French drain. It’s important to clean it once a year to remove any buildup of debris. While you can rent an electric sewer snake to clear it yourself, it’s easier to hire an expert because it requires multiple people to operate. 

Can you connect your French drain directly to your downspout?

The short answer is no. Your drainage system can become overwhelmed with water during a heavy storm, washing away gravel and clogging the system.

However, there’s a solution: If you need drainage for your downspout and want to utilize a French drain, simply install a catch basin between the downspout and the drain. A catch basin will prevent flooding and act as an easy-to-clean collection point for leaf debris. 

Get help from a pro

If the French drain installation process seems too tough to take on by yourself, or if you run into a problem with power lines or a rocky foundation (literally), it’s best to call a landscaping professional

You might have French drain installation covered, but what about the rest of your lawn? Drain installation may have left it in a sorry state. A Lawn Love team can take care of yard maintenance like maintenance, mowing, seasonal cleanup, and plant installation. 

Main Photo Credit: Shutterstock

Rachel Abrams

Born and raised in Gainesville, Florida, Rachel Abrams studied creative writing at the University of Virginia. She enjoys volunteering at her neighborhood community garden and growing herbs in her New York City apartment.