Quite simply a French drain is a trench filled with gravel and sand that enables water that would otherwise pool to drain away.
Although well established French drains are difficult to trace without digging they will generally be in two major positions.
High Point to Low Point
The first you will find them in is going from the high point of an area to the low point. This type of drain is designed to encourage excess water to drain away without pooling.
Across the Flow
The second position you will find a French drain is across the path of water that flows from adjacent properties designed to divert the flow sideways.
The drains work by providing excess water with an easy route to follow. The thin soil cover of the drain allows all the water to drain through easily and the sand and gravel mixture is no obstacle to the flow of water along the drain.
French drains need to be built on a grade to speed up the disbursement of water but ideally they should not be used to move one person’s problem to the property of another.
French drains are very efficient and need no maintenance and can make ideal yard drainage.