When filling the area around the inlet grate temporarily cover the grate to prevent any stones or soil from falling in after installing the french drain.
Installing french drain behind retaining wall.
Otherwise water moving down the hill will build up behind the wall and undermine it.
If you re building a retaining wall add a french drain behind the first course of stones or blocks.
For proper drainage the first 12 inches of space behind a retaining wall should be filled with crushed stone or gravel.
This video shows you how to properly install a drainpipe behind your wall for prop.
Fill the trench with topsoil and compact to completely cover the entire french drain system.
Mar 19 2014 when building a retaining wall lay perforated drainage tubing at the base of the wall slightly above ground level so runoff can drain out without undermining your wall.
The pipe should rest on the same compacted gravel base or concrete footing that supports the wall.
Typically drain lines are installed at the base of new walls before the soil is backfilled.
Check out this video for some simple instructions on installing a french drain behind an 18 to 24 tall retaining wall before it is backfilled with dirt.