a French drain is perforated pipe surrounded by gravel. It is used to remove water from low spots in the yard, under the your home in the crawlspace or basement.
A trench is dug and a base of gravel is laid in the bottom. Then the perforated pipe with holes pointing down is laid onto of the gravel, then more gravel is added on top of the pipe. Sometimes its encased in a geo – fabric. Depending on the application.
See Photos below..
In this application, Geo – Fabric is used to surround both gravel and pipe. This is a Yard Drain in sandy soil.
Note : Clay based soils, may not need this fabric.
Remember, The French Drain is used to collect water from Subsurface areas..
Catch Basins are used to collect immediate surface water runoff, or standing water in the yard.
Discharge of the French drain
Once the water has been collected by the French drain system, it needs to flow away from the area, preferably to the street or storm. There are 2 ways to do this.
1st is GRAVITY. if there is downhill fall away from the French drain (Low Spot) a trench is dug and solid pipe is laid to the point of discharge.
2nd is a Sump Pump. if the is no downhill flow away from the French Drain (Low Spot) then a hole is dug for a sump basin and a sump pump is installed. The water from the French drain is collect in the sump basin, usually 2 feet deep. The sump pump lifts the water up and pumps it to the point of discharge.
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See also: Crawl Space Footer Pipe