Installing French Drains

Step 1. From the lowest point of the area of the flooding area, you want to dig down to where the top of the catch basin is even with the top of the soil.

Step 2. The drainage ditch should be dug approximately 18” wide and slope downward at 1” per every 12 feet. This will give a gradual flow of water through the pipe without causing erosion from fast moving water. You should have at least a 12 foot drain line and upwards of 18-20 feet for areas with larger flooding.

The ditch should be approximately 2 inches deeper than the pipe attachment part of the catch basin.

Step 3. Lay gravel in trench

Step 4. The filter sleeve goes over the perforated pipe to keep the drainage holes from filling with dirt. The Pipe should be placed in the trench and attached to the connection area of the catch basin.

Step 5. So that you do not knock the pipe off the catch basin you want to carefully add the gravel to cover the pipe. Be sure to add gravel at least 2 inches past the end of the pipe opposite the catch basin. This will ensure that when water flows through the pipe it does not cause a wash out but it deterred by the gravel.

Step 6. Replace top soil over the drain line.

Illustration of French Drains

Following are illustrations of proper and improper installs of French Drains.

French Drain Properly Installed

French Drain Improperly Installed