Download Drain Pipe Behind Retaining Wall Pics. I would definatly put in the drain pipe even if it is only 2' tall. When you are installing the landscaped earth, which the retaining wall is designed to hold up, you should fit in some pvc pipes.
Making a block retaining wall;
An example drainage system could include backfilling with gravel, using drain pipes, and using weep holes to allow water to pass through the wall. Building a retaining wall requires a section (not the full backfill) to be drained. Taller walls may require more than one drain pipe to sufficiently relieve the hydrostatic pressure. Second, is having a perforated pipe.