Building a Simple Yard Drain: French Drain, Channel Drain, or Dry Well

A 7×5 yard backyard pooling water under a deck needs a drainage system. Options depend on where water can legally discharge.

Assess Discharge Point

5 yards away: is there a storm drain, swale, street gutter, or lower lawn area? Confirm it's legal to direct water there.

Option 1: French Drain (Best for Subsurface Water)

1. Trench from low spot to discharge (min 1% slope).
2. 4" perforated pipe (sock-wrapped) in 12" wide trench.
3. Surround with washed 3/4" stone, wrap with filter fabric.
4. Backfill with soil. Strainer at inlet, open at outlet.

Option 2: Channel Drain (Best for Surface Water)

• Trench across patio/deck threshold.
• Install pre-sloped channel drain kit (NDS, PolyLok).
• Grate flush with surface. Connect to 4" solid pipe to discharge.

Option 3: Dry Well (If No Discharge Point)

• Excavate 4×4×4 ft pit at low spot.
• Line with fabric, fill with clean stone.
• Pipe from inlet to stone. Water percolates down.
• Check local codes—some prohibit.

Tools

Line level ($5) on string to verify slope. 6" fall per 100 ft minimum.

Safety

Call 811 before digging. Watch for irrigation, electric, gas lines.

French drain is most versatile for yard ponding. Channel drain if water enters at hardscape edge.