I would like to install a couple more of these wall drain pipes on a side of the same front yard retention rampart that has bulged over the years, which I attribute to their lack.

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Is it enough if these (1-1/4 or 1-1/2" pipes) go barely deeper than the brick (one layer of brick = 4") to reach the dirt behind or do they need to go deeper?

1 Answer 1


Unless they are perforated, there is no reason for them to go deeper than the inside of the wall. You are installing them to relieve the hydrostatic pressure on the wall. Pushing them back deeper into the ground behind the wall may allow them to drain up-hill water easier, but if water builds up behind the wall anyway, then you still have the problem of the water pressure pushing on the wall.

Think of a dam. The force/pressure on the dam is only related to the height of the water behind the damn. How long the reservoir is behind the dam has no effect on the forces on the dam.

  • +1 for knowing that the size of the lake behind the dam has nothing to do with the stress on the dam. It’s only the depth of the water at the dam wall.
    – Lee Sam
    Sep 3, 2021 at 23:39
  • High school physics <wink>!
    – SteveSh
    Sep 4, 2021 at 0:45
  • is this called "french drain"?
    – amphibient
    Sep 5, 2021 at 3:06

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