French drains are an effective solution for managing excess water and preventing soil erosion, but installing one for the first time can feel intimidating. At Lyngso, we understand the challenges of outdoor landscaping and hardscaping projects. That’s why we’re here to advise you on how to build a French drain step-by-step. We will also provide links to the necessary tools and materials to install a DIY French drain in your outdoor space.
What is a French Drain?
A French drain is a gravel-filled trench containing a perforated pipe along its bottom. This construction redirects surface and groundwater away from a specific area, which helps with excess water management and prevents soil erosion. French drains can blend seamlessly into the surrounding landscape when designed and installed properly, adding a functional and aesthetically pleasing touch.
How to Install a French Drain DIY
Before installing the French drain, you will need certain materials and tools. These include a perforated pipe, drainage fabric, gravel or crushed stone, and digging equipment such as a trenching shovel. Some additional equipment, for example, a level and marking paint or flags, will also come in handy.
Step 1: Choosing the Location
Determining the location to install a French drain requires careful assessment of the site’s topography, water flow patterns, and drainage needs. Start by observing where water pools after rainfall and how it drains away. These observations will help you identify any low-lying areas that require drainage. We recommend installing the French drain downhill from those areas to ensure adequate flow and discharge of water. Another critical factor for choosing a suitable installation site for your French drain is its proximity to a convenient location for water disposal. Some options include stormwater catch basins, drainage ditches, the front of your house, or near a sidewalk. Ensure the water drains away from any buildings.
Step 2: Excavating the Trench
Before you get started with digging the trench, make sure that you are aware of the location of underground utilities. Call 811 before digging to avoid installing a French drain near gas, electrical, or sewer lines. Using a shovel or the digging tool of your choice, dig a trench approximately 9-12 inches wide and 18-24 inches deep. Make sure the bottom of the trench is level. The dirt you dug out is not needed for this project and can be used to create mounds for native gardens, or repurposed and amended in your landscape, or as a last resort, disposed of according to your local regulations and requirements.
Step 3: Lining the Trench with Filter Fabric
Lining the trench of a French drain with a quality drainage fabric ensures its proper functioning and longevity. The filter fabric prevents soil and debris from clogging the perforated pipe and blocking water flow. This addition will significantly reduce the need for future maintenance. To line the trench with the drainage fabric, place it in its bottom, ensuring it covers the entire area and overlaps the sides.
Step 4: Installing the Perforated Pipe
Now it’s time to lay a length of perforated pipe along the bottom of the trench. Place the perforated pipe on the filter fabric making sure it is centered. You can use connectors to join multiple tube sections if the trench is long. We recommend using fully perforated drain pipes instead of PVC ones with holes at the bottom. Fully perforated corrugated pipes are resistant to clogging and more permeable, moving water faster. If you are looking for a high-quality perforated pipe, be sure to check out Ewing Irrigation. They offer different sizes and configurations of perforated pipes to suit your specific French drain requirements.
Step 5: Adding Gravel or Crushed Stone
Add gravel or crushed stone to the trench without filling it entirely. Our stone recommendation for French drains is the fantastic 3/4″ Crushed Drain Rock which you can order from our store. It provides excellent drainage, prevents the trench from collapsing, and offers the necessary structural support to the pipe. Although you can use other rocks, such as pea gravel, make sure they are free of dust or organic material that could clog the pipe and prevent water flow.
Step 6: Wrapping and Filling the Trench to the Top
The last step of this DIY French drain installation is to burrito-wrap the gravel or crushed stone we added in step 5 using the filter fabric that overlaps the sides of the trench. Then add the rest of the rock until the trench is full. This construction will ensure adequate filtration and contribute to the longevity of your French drain. Alternatively, you can backfill the trench with some of the sod you dug in step 1. Although we recommend using a quality drainage rock, topping the trench with sod is also an option, depending on the aesthetic you aim to create.
Installing a French drain on your property can be a rewarding and cost-effective project that helps manage excess water and enhances the look and functionality of your outdoor space. With a variety of tools and drainage stones available by Lyngso, you can create the perfect French drain for your needs and budget. Remember that you can visit our large showroom and landscaping yard in San Carlos for more ideas, and contact us today to learn about delivery options for your SF Bay area home.
