How to Install a French Drain in Your Yard

A French drain is an underground drainage system that collects and diverts subsurface water away from problem areas. To install a French drain in your yard, start with gravel, non-woven geotextile fabric, and perforated pipe. 

As a landscape designer, I’ve installed French drains for homeowners, and together with our expert, we’ll share our pro tips — from trenching and sloping to lining, graveling, and installing the perforated pipe.

Project difficulty: Intermediate Estimated time to complete: 2 days, or over the weekend Project cost: Depending on the project’s scope and your yard’s size, professional French drain installation costs an average of $5,000, with most homeowners paying between $1,650 and $12,250.

If you’d rather not tackle installing a French drain yourself, hire a local LawnStarter landscaping pro. They have the skills, knowledge, and equipment to dive into the trenches and get the job done right.

Gather Tools and Materials

To prevent unforeseen trips to the home improvement store, here’s a basic list of tools and materials to have on hand before you begin:

Excavation

• Wheelbarrow
• Trenching shovel: for digging
• Pickaxe/pick mattock: to break up rocky or compacted soil and cut through roots
• Grub hoe: smooths soil at the trench bottom
• Trencher machine (optional)

Drainage

• 4-inch HDPE double-wall corrugated pre-slit pipe
• Gravel: 3/4 to 1 1/2 inches
• 9-inch x 9-inch catch basin and grate
• Catch basin adapters
• Non-woven geotextile fabric
• Clear waterproof silicone

Pipe connection

• Tile tape
• HDPE 4-inch external couplers
  

Other tools and materials

• Utility knife (to cut fabric)
• Hacksaw (to cut pipe)
• Power drill with 1/4-inch bit
• Topsoil and grass seed (optional)

Plan Your Project

• Permits and permissions: Ensure safety and compliance by checking for necessary permits from your municipality and/or HOA. 
• Utilities: Call 811 to mark underground utility lines. This is a national call center to contact before you dig.
• Check your area’s frost line and building requirements: “Consult with local building codes to ensure adherence to regulations and to understand what works well for your region,” says Damon Abdi, assistant professor of landscape horticulture at Louisiana State University. Installing below the frost line prevents the pipe from moving as the soil freezes and thaws.

Safety Tip: If you live in the northern half of the country, it’s better to hire a drainage professional to install your French drain. Deep trenches require commercial equipment and can collapse in rare cases, causing injury or death.

Determine the French Drain Location

Choose a location that:

• Has noticeable standing water
• Has a natural slope to guide water away from your home
• Is free of large tree roots, boulders, and buried utilities

Note: Avoid directing water onto neighboring properties to prevent liability or drainage disputes.

Mark the Area

• Use a 100-foot tape measure to mark a straight line along your intended trench. (Spray paint or stakes and string work well to outline the trench location.) 
• Ensure your trench starts at a high point and slopes down to a lower drainage point.

How to Install a French Drain

With the proper tools, materials, and planning, you’re now ready to begin installing your French drain. 

Protect Your Grass 

Place plywood planks or wooden boards on your lawn in areas where you will be transporting materials with a wheelbarrow and/or using a trenching machine. This will help prevent muddy tire tracks and protect your grass from damage.

Dig the Trench

Generally, the trench should be between 1 and 1 1/2 feet wide and 1 1/2 to 2 feet deep. However, the frost line in your area — “anywhere from about a foot to several feet deep,” says Abdi — will help you determine whether you want to dig by hand or use a trenching machine. 

“It is also important to consider where that French drain will drain from (i.e., around a foundation or in the middle of the yard), as drains installed near a foundation may have their own set of codes,” he says.

Pro Tip: If you’re able, dig out the sod with a flat-edge shovel or sod cutter before you start trenching. When you’re finished installing the drain, you can replace the sod to maintain a seamless look in the lawn.

My Experience: About 30 years ago, we installed a 100-foot French drain in our Pennsylvania backyard. The 4-foot-deep, 2-foot-wide trench (to clear the 44-inch frost line) used corrugated and PVC pipe with a catch basin.

Know the Slope

Because a French drain relies on gravity to move water, the trench must be dug with the correct slope. Getting this grade correct is essential — be sure to check your building codes. 

Recommended Slope: Abdi says, “A slight slope (1%, or roughly 1-inch drop per 8 feet) is the minimum recommended by many installers; however, the preferred slope may vary by the type of pipe being used.”

Too Little Slope: Water drains slowly, causing standing water in the pipe and potential flooding.

Too Much Slope: Water flows too fast, leaving debris behind, risking clogs, and potentially causing erosion at the outlet.

Measure the Pipe Length

Start by measuring the trench while factoring in any curves, bends, and slopes. This will give you an accurate estimate of the amount of pipe required for installation.

For most residential projects, 4-inch HDPE double-wall corrugated pre-slit pipe is sufficient. Abdi says, “Pipe sizing varies by the site conditions (i.e., soil texture, impervious surfaces, on-site drainage patterns), but generally a 4-inch diameter pipe (is) suitable for most home applications.”

Most pipes are available in 10- or 25-foot sections, so it’s a good idea to purchase a little extra (10%) to accommodate any adjustments. 

Install Non-Woven Geotextile Fabric 

Line the trench with non-woven geotextile fabric, leaving 10 inches of extra fabric on either side of the trench. This fabric helps prevent soil from clogging the system over time.

Add Gravel

Pour about 3 inches of gravel evenly along the bottom of the trench. This helps with filtration and pipe stability.

Lay the Pipe 

• Set the perforated pipe on the gravel with the holes pointing downward. This allows water to enter from the trench bottom and flow up into the pipe. It may seem counterintuitive, but this way the pipe captures underground water rather than surface runoff.
• Start from the catch basin, adding couplers as needed. 
• Use tile tape to secure the couplers and ensure a tight, water-resistant seal.

Connect the Catch Basin

Drill four small holes in the basin’s bottom corners to allow residual water to drain. Use silicone and adapters to secure the pipe to the basin according to the manufacturer’s instructions.

Test the Flow 

A 100-foot run of 4-inch pipe and a 1% slope can typically handle about 5 gallons per minute (GPM), meaning 1 gallon of water should drain in roughly 12 seconds under ideal conditions. 

Add More Gravel

Backfill around the pipe with gravel up to a few inches below the surface. Don’t overfill — leave room to backfill with soil or place the sod pieces back on top.

Fold Over the Fabric

Fold the fabric over the gravel, like wrapping a burrito, and secure with landscape staples. This keeps debris from getting in and clogging the system.

Backfill with Soil

Add topsoil or sod pieces over the trench, and plant grass seed if needed.

FAQ

Protect Your Home from Water

Installing a French drain is one of the most effective ways to protect your yard and home from excess water. With the right tools and some planning, it’s a DIY-friendly project for many homeowners. But if you’d rather leave it to the pros, hire a local LawnStarter landscaping pro to handle it for you.

See Related: What is a French Drain?

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