Where the water actually goes

Step by step

1. 1Rain. Rain falls on the ground above and behind the wall. A wall does not hold back water — it holds back soil, and the water is what makes that soil heavy.
2. 2Infiltration. The water soaks down through the retained soil. Saturated soil can weigh roughly half as much again as dry soil, and it pushes on the wall the whole time it stays wet.
3. 3Drain rock. Behind the blocks sits clear drain rock, with filter fabric between the rock and the native soil. The water runs freely down through the rock instead of building pressure against the wall.
4. 4Pipe collection. The perforated pipe sits in the base, at the lowest point the water can reach — not up behind the first block. Set any higher and it only drains what rises to meet it.
5. 5Outlet. The pipe runs to daylight and the water leaves the wall. Every part of this is buried and invisible once the job is done, which is exactly why it gets skipped.