A 40-foot French drain installed to redirect water from a chronic low spot in a Virginia backyard. Covers grading assessment, pipe installation, and outlet options.
A low area in the backyard where water pooled after every rain and remained soggy for days. Virginia clay soil drains slowly — water has nowhere to go. The pool area was roughly 15×10 ft and the surrounding grade sloped slightly toward it from two sides. Adjacent to a wood fence that was showing rot from constant moisture exposure.
First step before digging anything: spend time with a level to confirm where the water needs to go and verify there's an outlet. In this scenario, water could drain to the street via a 40-foot run along the property line.
| Material | Quantity | Cost |
|---|---|---|
| 4" perforated drain pipe (with sock) | 50 ft | $55 |
| Washed gravel (3/4", clean) | 1.5 tons | $90 |
| Filter fabric (non-woven) | 1 roll (100 sq ft) | $30 |
| Solid 4" drain pipe (outlet run) | 15 ft | $20 |
| Pop-up emitter (outlet) | 1 | $15 |
| Pipe connectors & fittings | — | $25 |
| Topsoil (backfill) | 5 bags (40 lb) | $25 |
| Sod (patch over trench) | 4 sq ft | $15 |
| Trench spade rental (half day) | — | $35 |
| Total | ~$310 + misc ≈ $400 | |
Call 811 (Dig Safe) at least 3 days before digging to have utilities marked. In Virginia, this is free and required by law. Then walk the drain route with a level to confirm consistent slope toward the outlet. Minimum: 1% grade (1 inch drop per 8 feet run).
Dug a trench 12 inches deep and 12 inches wide along the planned route. In Virginia clay, a trench spade is much more effective than a regular shovel. The trench starts at the low spot (12 inches deep) and maintains slope to the outlet where it daylight at 4–6 inches deep.
Lined the trench with filter fabric, leaving excess fabric on the sides to fold over the top. Added 3 inches of washed gravel at the bottom. Gravel must be washed (no fines) — dirty stone clogs drain pipe quickly.
Laid 4-inch perforated pipe (with fabric sock already installed) on the gravel bed, holes facing down. Connected to solid outlet pipe at the far end. Covered pipe with 6 more inches of washed gravel. Folded filter fabric over the top of the gravel to prevent soil migration into the system over time.
Covered fabric and gravel with 2–3 inches of topsoil. Patched with sod over the trench. Installed pop-up emitter at the outlet, set flush with grade. Pop-up emitters open under water pressure and close when flow stops — prevents debris and animals from entering the pipe.
The same principles apply — read the full retaining wall guide which covers drainage in detail.
Retaining Wall Guide →