How to Install a French Drain in a Driveway

French drains are also known as dry wells, due to the design similarities in both the drain and the water well. Dry wells have been used for over a century to collect runoff water and divert it away from the foundation of a house, patio or driveway. French drains may be constructed with pre-manufactured parts or made using only materials traditionally used in construction work.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Shovel
• Hose and water
• Measuring tape
• Graph paper
• Small wooden or plastic stakes
• Peas-sized gravel
• Broken clay pottery shards or stone chips
• Gravel
• PVC pipes with connectors (optional)
• Thick gardening fabric
• Metal gardening stakes

1. Measure the driveway area to determine possible locations for the dry well(s). Large driveways may need more than one well to effectively move the water from the hardscape. Transfer the measurements to the graph paper.

2. Conduct a perk test on the areas selected for the French drain. Start with an area that is most suitable, based on the landscape design. Dig a hole at least 4 feet deep, then insert the hose and fill the hole with water. Time the water as it absorbs into the soil. The ideal absorption is 3 inches per minute. If the drainage does not meet this standard, select a new area and continue with the absorption tests.

3. Allow the hole to sit until the soil is moist, not wet, and then begin constructing the well. Place at least 3 inches of the broken clay pottery shards or large stone chips on the bottom of the well.

4. Line the well with the thick gardening fabric.

5. If the well must be located some distance from the drive; (due to absorption capabilities) a one-foot deep trench must be dug from the drive to the well. Dig the trench at least six inches wide and allow the trench to slope toward the dry well. The runoff water will be diverted into the PVC pipe. Punch out one of the round perforations in the plastic casing and insert a PVC connector to install the pipe from the drive.

6. Insert the plastic well casing into the well. Be sure to push down on the casing so that it sits evenly on the large shards.

7. Add the pea-sized gravel to the sides of the well opening. Make sure that the gravel does not wedge into the plastic casing in between the fabric, since this would reduce the effectiveness of the well.

8. Cover the top of the gravel with more garden fabric. Secure the fabric edges with the gardening stakes to keep any topsoil from entering the well.

9. Insert the well grill to cap off the top and construct the driveway.

Tips & Warnings

• If the drive has not been excavated, do a perk test in various areas of the yard to determine the best place to locate the French drain. Retain the graph paper with the drain measurements. These will come in handy should the drain need to be replaced or for future yard work.
• French drains constructed using traditional materials are not as durable as those built with plastic well inserts. All drains will need to be replaced at some point due to erosion during use, but the plastic inserts will prolong the viability of the dry well. Some properties will not have soil suitable for a French drain. The perk test is critical to determine the suitability of the ground.

References

• What is a French Drain?

Resources

• Video Building Demonstration
• Video Digging a French Drain