French Drain Installation
A French drain is a gravel-filled trench with a perforated pipe that redirects surface water and groundwater away from our client's foundation. Here's how to properly install one.
Step 1: Double-Check Utility Marking
Ensure 811 has been called and all public utility markings are flagged and confirmed before beginning excavation.
Step 2: Excavate the Trench
Follow the excavation procedure to dig a trench with at least 1% slope. The bottom of the trench should be flat and smoothed out with no high or low spots. If catch basins will be installed in this system, excavate an extra 4-6" on each side of the trench where the basins will be placed.
Step 3: Lay Filter Fabric
Place filter fabric across the trench and secure it using landscape pins. Ensure the bottom of the trench remains flat while doing this step.
Step 4: Install Pipe
Place perforated pipe at the bottom of the trench. The perforated pipe should always be installed at the bottom of the trench. Do not combine French drains with downspouts discharge lines or catch basins discharge lines. Include tracer wire in the trench if required, and ensure all pipe connections are made securely. In this complex example, 2 black perforated pipes (for the French drain) are placed under 2 blue solid pipes (for catch basins and downspouts).
Step 5: Add Gravel
Fill the trench with gravel until it reaches 4–6" below the soil surface. If the system is meant to be an "open French drain", fill the trench all the way to the top with gravel.
Step 6: Wrap With Fabric
Fold the excess filter fabric over the top of the gravel. Trim any overlap greater than 2 inches to maintain a clean installation and proper flow, and remove areas of fabric that cover catch basins. Secure with landscape pins.
Step 7: Backfill
Finish the installation by adding 4–6" of soil over the fabric, following the "backfill" procedures.