How to install a simple French drain to redirect surface water
A simple French drain can protect your yard, foundation, or low spots by redirecting excess surface water away from problem areas. This guide walks you through a straightforward weekend project using common tools and materials to create a shallow, surface-level French drain. Take your time measuring and sloping correctly — small differences make a big performance improvement.
Step 1: Plan the drain route
Identify the wettest spot and a suitable discharge point at least 10 feet away, such as a storm drain, dry well, or downhill area. Walk the path and mark a fairly straight line using spray paint or stakes and string; keep the slope between 1% and 2% (about 1/8 to 1/4 inch drop per foot) to ensure steady flow. Consider underground utilities and call 811 before digging.
[Illustration: diagram of yard with marked line, stakes, string, and arrows showing slope and discharge point]
Step 2: Gather materials and tools
Buy 4–6 inch perforated PVC or corrugated pipe (1 linear foot per foot of trench), landscape fabric, 3/4 inch clean gravel, a shovel, tape measure, level, wheelbarrow, and gloves. For a typical 25-foot trench expect 25 feet of pipe, about 0.5 cubic yards of gravel, and one 3- to 6-foot roll of fabric. Renting a trenching shovel or small trencher saves time for longer runs.
[Illustration: pile of perforated pipe, gravel bags, landscape fabric, shovel, level, and wheelbarrow on lawn]
Step 3: Mark and lay out slope
Use the stakes and string to create a visual guide for the trench slope; set the upstream stake higher and lower the string toward the discharge point to achieve 1/8–1/4 inch per foot. Double-check slope with a line level or a long straight board and a torpedo level every 10 feet. Correct slope now to avoid rework after digging.
[Illustration: close-up of string line with small line level and measuring tape showing slight downward pitch]
Step 4: Dig a shallow trench
Dig a trench 6–8 inches wide and 12–18 inches deep along the marked route, keeping the bottom smooth and maintaining the planned slope. For a surface-level French drain aimed at redirecting runoff, 12 inches deep is usually sufficient; deeper trenches are needed if routing around foundations. Place excavated soil on a tarp for easy backfill and to avoid mixing topsoil with gravel.
[Illustration: worker digging narrow trench with shovel next to tarp holding excavated soil]
Step 5: Create gravel base and fabric liner
Add a 2–3 inch layer of 3/4 inch clean gravel to the trench bottom and compact lightly to form a stable base that promotes flow and prevents pipe settling. Line the trench sides and bottom with landscape fabric, leaving 12 inches extra on each side to fold over the gravel later; the fabric keeps sediment out while allowing water to pass.
[Illustration: trench with gravel base and landscape fabric lining with edges folded back over sides]
Step 6: Install perforated pipe
Lay the perforated pipe on top of the gravel with holes facing downward or sideways to encourage water entry, connecting sections with couplers and securing joints with silicone if using corrugated pipe. Ensure the pipe follows the trench slope and extends 6–12 inches beyond the downstream gravel to discharge; for visible outlets, install a small pop-up drain or rock splash pad at the exit.
[Illustration: perforated pipe being placed into lined trench with visible slope and joined sections]
Step 7: Cover, fold fabric, and finish
Cover the pipe with 2–3 inches of gravel, then fold the excess landscape fabric over the gravel to create a sediment barrier. Backfill the remaining trench with topsoil or decorative stone; if replanting grass, add 3 inches of topsoil and sod or seed. Water the area lightly and monitor after the next heavy rain to confirm the drain redirects water as intended.
[Illustration: finished trench covered with gravel and folded fabric, topsoil and grass on sides, outlet area with rock pad]
- Call local utilities (811) at least 48–72 hours before you dig to locate underground lines.
- Maintain a consistent slope of 1/8–1/4 inch per foot; use a string line and level for accuracy.
- Use clean 3/4 inch crushed stone to avoid clogging; do not use river rock or pea gravel as the void space differs.
- For 25 linear feet of 4–6 inch pipe expect roughly 0.4–0.6 cubic yards of gravel; buy a bit extra to allow for compaction.
- If near a foundation, keep the trench at least 2 feet away from the wall or slope soil away from the structure when backfilling.
- Inspect the exit point seasonally and remove debris; consider adding a PVC elbow or grating to reduce erosion at the outlet.
- Do not dig before calling 811 to avoid striking buried utility lines — this is both dangerous and illegal.
- Avoid perforated pipe in areas with heavy sediment or clay runoff without additional filtration because the pipe can clog; consider a solid outlet section or professional advice for high-sediment sites.
- Do not pitch the drain toward a neighbor’s property without permission; redirecting water onto someone else can create legal disputes.
- If you encounter standing groundwater or suspect you need deep drainage near foundations, consult a licensed drainage contractor; a shallow French drain is not a cure-all for water table or basement seepage.
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