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How To Install A French Drain

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Eugene Kushmarak

Please meet Eugene, one of our basement flood experts. He started his career from the bottom, digging trenches, working his way up to contractor, supervisor. Learn More About Eugene Kushmarak

A French drain is a straightforward solution for areas that get too wet. It’s a trench filled with gravel or rocks and has a special pipe that helps move water away from your house, reducing the risk of water damage and erosion.

Installing a French drain helps control water flow, prevents basement flooding, and keeps the foundation of your home dry. The installation involves digging a trench, placing a fabric mesh and gravel, setting a perforated PVC pipe, and then covering it back up with soil and gravel.

Keep reading for a step-by-step guide to installing a French drain and tips to improve yard drainage with Aquatech Waterproofing!

How to Install a French Drain in Your Yard

Installing a French drain can effectively alleviate water pooling and improve yard drainage. Here’s a concise, five-step guide to implementing this system:

1.  Planning and Preparation:

  • Assess Your Landscape: Survey your yard to identify areas with poor drainage. Using a line level or a transit level, determine the path from the highest point of water collection to an appropriate exit point, ideally where water can drain without causing issues.
  • Regulatory Compliance: Before digging, ensure compliance with local building codes and regulations. Contact your local utilities to mark any underground lines and avoid potential damage during excavation.
  1. Trench Excavation:

  • Digging the Trench: Outline your trench path with landscaping paint or stakes and string. The trench should be approximately 12 inches wide and 18-24 inches deep, maintaining a consistent downward slope (at least 1% grade) towards the exit point. Use a trenching shovel or a trencher machine for effective excavation.
  • Safety Considerations: Secure the sides of your trench to prevent collapse, especially in sandy or loose soil conditions.

3. Installing the Drainage System:

  • Landscape Fabric: Line the trench with a non-woven geotextile fabric to keep the drain free of silt and debris. Ensure the fabric extends beyond the edges of the trench.
  • Gravel Bed: Fill the trench with about 2-3 inches of washed gravel to create a stable base for the pipe.
  • Pipe Placement: Lay a perforated drainage pipe along the length of the trench on top of the gravel. Ensure the perforations face downward to prevent clogging and maximize water capture.
  1. Backfilling the Trench:

  • More Gravel: After placing the pipe, cover it with additional gravel until the trench is filled to within 5 inches of the surface.
  • Fabric Closure: Fold over the excess landscape fabric over the top of the gravel to provide an added layer of filtration.
  • Soil and Restoration: Fill the remaining space with the excavated soil, tamp it down lightly, and restore the surface with grass seed or sod to blend with the existing lawn.
  1. Maintenance and Testing:

     

  • Initial Testing: Before completing the fill, conduct a test by pouring water into the drain to ensure it flows correctly and exits where intended.
  • Ongoing Maintenance: Inspect the drain exit and entry points regularly, especially after heavy rainfalls, to ensure they remain clear of debris and operational.

By following these steps, your French drain will effectively redirect excess water, protecting your landscape and foundations from moisture-related damage.

Materials Needed for Installing a French Drain

To successfully install a French drain in your yard, you will need several key materials:

  1. Perforated Drain Pipe: Choose a flexible perforated pipe, typically made of PVC, which allows water to enter through small holes along its length.
  2. Gravel: Coarse, washed gravel is essential for covering the pipe and facilitating effective water filtration and drainage.
  1. Landscape Fabric: Non-woven geotextile fabric helps prevent soil from clogging the gravel and pipe, ensuring long-term functionality of the drain.
  2. Trench Shovel or Trencher: A trenching tool is necessary for excavating the soil to form a uniformly deep and narrow trench.
  3. Level: A line level or laser level will help ensure your trench has the proper slope for effective drainage.
  1. Utility Knife: Useful for cutting the landscape fabric to size.
  2. Stakes and String: These are used to mark the trench path accurately before digging.

Collecting these materials before you begin will streamline the installation process, ensuring your French drain is built efficiently and functions properly to manage water flow in your landscape.

How Much Does It Cost to Build a French Drain?

The total cost of building a French drain varies depending on materials and length. Below is an estimated cost breakdown for constructing a standard French drain with a 6-inch diameter, 10-foot-long perforated drain pipe:

Material Estimated Cost
Perforated Drain Pipe $20-$40 per 100 feet
Gravel $30-$50 per cubic yard
Landscape Fabric $20-$30 per 100 square feet
Trench Shovel or Trencher Shovel: $30-$50, Trencher rental: $75-$100 per day
Level $10-$25
Utility Knife $5-$15
Stakes and String $5-$10
These prices are approximate and can vary based on location, supplier, and specific product choices. It’s a good idea to shop around or rent some of the more expensive items, like a trencher, to keep costs down. Gather all materials ahead of time to ensure the installation process goes smoothly.

How To Measure the Slope for a French Drain in Your Yard

For French drains to function effectively, they require a minimum 1% downward slope — this means a one-inch drop for every ten feet of length. Here’s how to determine if your yard has the necessary slope:

  1. Prepare Your Tools: Get two wooden stakes, each about 36 inches long. Mark these at one-inch intervals, effectively turning them into large “measuring sticks.”
  1. Position the Stakes: Drive the stakes into the ground at the start and end points of where you want your French drain. Ensure each stake is buried to the same depth, between six and twelve inches.
  2. Set Up the String Line: Stretch a string tightly between the two stakes. Attach the string at a point on the top stake that is just above ground level and adjust it on the bottom stake so that the string is perfectly horizontal. Use a carpenter’s level to ensure accuracy.
  1. Measure the Slope:
    • Vertical Measurement: At both stakes, measure the distance from the ground to the string. Subtract the measurement of the top stake from the bottom stake to find the vertical change (rise).
    • Horizontal Measurement: Measure the length of the string itself to determine the horizontal distance (run) between the two stakes.
  1. Calculate the Slope: Divide the rise by the run and multiply by 100 to express the slope as a percentage.
  2. Assess the Results: If the calculated slope is 1% or more, your yard is suitable for a French drain without needing adjustments for depth. If under 1%, you’ll need to dig the trench deeper as it runs downward to create an adequate slope, likely requiring extra gravel and topsoil to fill in the deeper sections.


Using this method will help ensure that your French drain is installed with the appropriate slope for optimal drainage.

How Do You Maintain a French Drain System?

Once your French drain is in place, regular maintenance is key to its continued effectiveness in diverting water away from your property. Periodically inspect the drain for any signs of clogs or accumulation of debris within the pipe. Keep an eye out for erosion or soil displacement around the trench, as these can lead to blockages. Should any issues arise, promptly address them. Here are some maintenance guidelines to follow:

  • Regularly inspect both the inlet and outlet (if applicable) of the drain to ensure unobstructed flow.
  • Flush out any debris every few months as needed to prevent blockages.
  • In the event of damage or disassembly of the drain, consider excavation and reassembly, especially if the drain is only covered with gravel and not topsoil and grass.
  • Additionally, maintaining proper functionality of the French drain system is essential. If water fails to drain as expected, consider adding more gravel or adjusting the trench’s slope to facilitate proper water flow away from your property.

Rely on Aquatech Waterproofing for Expert French Drain Installation!

Protect your property with the best defense against water damage. Aquatech Waterproofing specializes in French Drain systems that effectively manage and reroute water, keeping your basement dry and your foundation intact. Our experienced team guarantees precise installation and lasting results. Choose Aquatech Waterproofing for a drier, safer home. Trust the experts, trust Aquatech!

FAQs About Installing A French Drain

Before installing a French drain, it’s essential to mark the area where you plan to dig the trench. Remove any obstacles like rocks, roots, or existing piping from the path of the drain. Additionally, ensure you have proper drainage plans for where the collected water will be redirected.

While installing a French drain is feasible for some DIY enthusiasts, hiring a professional is often recommended for optimal results. Professionals have the expertise to assess your specific drainage needs, navigate potential challenges, and ensure the drain is installed correctly to prevent future issues.

The depth of a French drain typically ranges from 12 to 24 inches, depending on factors such as the soil type, the volume of water expected, and the depth of the water table in your area. It’s crucial to dig the trench deep enough to allow proper drainage without risking damage to underground utilities or compromising the drain’s effectiveness.

French drains can be installed in various soil types, including clay, loam, and sandy soils. However, the effectiveness of the drain may vary depending on the soil’s permeability. In clay soils, for example, drainage may be slower due to the soil’s compactness, while sandy soils typically allow for faster drainage.