Retaining Wall Drain Outlets

Retaining walls must be strong enough to hold back hundreds of pounds of soil. However, without a drainage system, even the strongest retaining wall will buckle. It is much easier to install a drainage system during the retaining wall's construction than to try to install one later on and then repair any damage the wall sustained. A retaining wall drainage system consists of a perforated pipe and gravel. The gravel allows water to flow easily into the pipe, which collects the water and guides it toward the retaining wall's end.

Gravel
Soil
Metal rake
Hand tamper
Landscape fabric
4-inch perforated pipe
Scissors

Instructions

- 1
  Build up the retaining wall's first three levels. Pour gravel behind the retaining wall. Spread the gravel into a 12-inch-wide 2-inch-deep layer, using a metal rake. Make one end of the gravel layer slightly higher than the other end to create a downward slope. Fill the area behind the gravel with soil. Tamp down the soil and gravel with a hand tamper.
- 2
  Unroll landscape fabric behind the retaining wall. Lay the fabric over the gravel and place a 4-inch perforated pipe on the fabric. You can use either flexible or rigid pipe. The pipe should touch the back of the retaining wall and extend approximately 2 or 3 inches past the gravel's low end.
- 3
  Pour gravel over the drainage pipe and spread it out to a 12-inch-wide 2-inch-deep layer. Fold the landscape fabric over to cover the gravel. Cut off any extra fabric with a scissors.

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