Standing water in your yard kills grass, breeds mosquitoes, and can seep into your foundation. A French drain is the classic solution — a gravel-filled trench with a perforated pipe that collects subsurface water and redirects it to a safe discharge point. It is one of the most effective drainage fixes a homeowner can install.

How to Install a French Drain

How a French Drain Works

Despite the name, a French drain is not French. It is named after Henry French, a Massachusetts farmer who popularized the technique in the 1850s.

The concept is simple: water flows downhill and follows the path of least resistance. A trench filled with gravel collects groundwater. A perforated pipe at the bottom of the trench captures the water and carries it by gravity to a lower point — a storm drain, a dry well, a swale, or daylight at the edge of the property.

Planning

Identify the problem area. Where does water collect? After a heavy rain, walk the yard and note the low spots, soggy zones, and water flow patterns.

Determine the discharge point. The drain must slope downhill from the collection area to the discharge point. You need at least 1 percent slope — a drop of 1 inch per 8 feet of run. Use a level and a string line to verify you have enough elevation change.

Call 811. Underground utilities are everywhere. Have them marked before you dig.

Check local codes. Some municipalities regulate where you can discharge collected water. You usually cannot direct it onto a neighbor’s property or into the sanitary sewer.

Materials

4-inch perforated PVC drain pipe with filter sock (the fabric sleeve keeps silt out of the perforations)
3/4-inch washed gravel or drainage stone
Landscape fabric (non-woven geotextile)
Solid PVC pipe and fittings for the discharge end
Catch basin (optional, for surface water collection)
Pipe fittings: couplers, elbows, end caps as needed

Tools

Shovels — a flat spade for cutting sod and a round-point shovel for digging
Wheelbarrow
Tape measure
String line and stakes
Level
Tamper

Digging the Trench

Mark the trench path with spray paint or stakes and string. The trench should be 12 inches wide and 18 to 24 inches deep. Wider and deeper is better, but these dimensions work for most residential drainage problems.

Maintain a consistent downhill slope as you dig. Check the grade frequently with a level on a long board laid in the trench.

Pile the excavated soil on a tarp to keep it off the grass. You will need some of it to backfill the top of the trench.

Lining the Trench

Lay landscape fabric in the trench, leaving enough excess on each side to fold over the top of the gravel later. The fabric acts as a filter — it lets water through but prevents fine soil particles from clogging the gravel and pipe over time.

Installing the Pipe

Add 2 to 3 inches of gravel to the bottom of the fabric-lined trench. Lay the perforated pipe on the gravel bed with the perforations facing down. This seems counterintuitive, but it works because water rises from below into the pipe rather than draining down from above.

If you are using pipe with a filter sock, the sock eliminates the need for landscape fabric around the pipe — but you should still use fabric to line the trench walls.

Connect the perforated pipe to a solid (non-perforated) pipe at the discharge end. You do not want the discharge section to leak water back into the ground before it reaches the outlet.

Backfilling

Fill the trench with gravel to within 4 to 6 inches of the surface. Fold the landscape fabric over the top of the gravel from both sides, overlapping in the center. This creates a complete fabric envelope that keeps soil out of the drainage system.

Backfill the top with the reserved soil and replace the sod or seed the area.

Optional: Adding a Catch Basin

If the problem area includes surface water pooling (not just subsurface water), install a catch basin — a plastic box with a grate on top — at the low point. Connect it to the French drain pipe with a solid PVC connection. Surface water flows into the grate and enters the pipe system directly.

Testing

After a rain, check the discharge point. You should see water flowing out of the pipe. If the system seems to not be working, check for slope errors or blockages at connections.

Maintenance

French drains are low maintenance. Flush the pipe with a garden hose once a year to clear any sediment. Keep the discharge point clear of debris, leaves, and soil buildup. If you installed a catch basin, clean the grate and box each fall.

A properly installed French drain lasts 15 to 30 years. It solves drainage problems permanently and protects your foundation, your lawn, and your garden beds from water damage.