How to Install a French Drain Outside

French drains allow drainage in yards that have few or no slopes. A french drain consists of a pipe with holes, which is surrounded by stone or peat gravel, and a filtered fabric that runs the length of the drain. French drains have a slight downgrade angle to help remove water and disperse it into an area that will not be damaged by the runoff water. The downgrade performs best at a 6-inch drop for every 50 feet of trench.

Things You'll Need

• Two stakes
• String
• Measuring tape
• Shovel
• Perforated plastic pipe
• Pipe glue
• Filter fabric
• Peat gravel
• Sod

Instructions

1. Place wood or metal stakes into the ground at the beginning and end of where the french drain will be located. The stakes should be deep enough in the ground to allow a string to be stretched taught from end to end without dislodging the stake.

2. Tie a string onto the beginning stake 1 foot from the ground.

3. Run the string to the opposite stake and tie it off at the correct height, which is determined by the 6-inch drop for every 50 feet of trench. For example, a string tied off 12 inches above the ground at the beginning of the trench will be stretched 50 feet and then tied off 6 inches above from the ground at the end of the trench for a level yard.

4. Dig the trench using a shovel. The depth of the trench should be between 16 inches to 3 feet deep, depending on how wet the ground is. The trench should be 12 inches wide.

5. Line the trench with yard fabric or a filtering fabric to stop soil and sand from penetrating the gravel that will be placed in the hole. Deposit a few inches of peat gravel into bottom of the hole and place a perforated plastic pipe in trench throughout the entire length of the trench. Use PVC pipe glue at the joints of the pipe if needed when connecting.

6. Once the pipe is laid out, fill the rest of the trench with peat gravel, leaving a 3-inch gap on top so that the filtering fabric can be folded over the peat stone. Finally, cover the folded fabric with sod to match the rest of the yard.

Tips & Warnings

• When the yard is not level or hills are present, use a transit level to determine the correct downgrade angle.

References

• French Drain Installation Tips