What are French Drains?
A configuration where perforated pipe or tubing is set below grade to catch water and then direct it away from the problem area.
The perforated pipe is set in a trench, in some cases the trench is lined with very heavy plastic to hold the water and accommodate the water entering the perforations in the pipe.
This can often be accomplished with a simple gravity flow of the water into a dry well, in some extreme cases pumping the water is necessary due to volume.
Once again filtering cloth must be used to keep sand from entering and clogging the french drain.