The water will still flow through the rocks with the pipe assuming your ditch slopes as well. If any sediment makes its way through or around the fabric, the extra 3″ will help prevent the sediment from going into the pipe.
Why do you put rocks in a French drain?
Proper drainage rock is crucial for adequate permeability and drainage. Using a clean natural round stone for your drain fill material enables good flow through the aggregate and won’t clog the system.
Do you put gravel under French drain?
The old way of installing French drains is to do it without the gravel and the fabric. Without the gravel and the fabric, however, the drain can clog up with sand and soil over time.
How deep should gravel be in a French drain?
Pour and compact about 3 inches of gravel or landscaping stone along the bottom of the trench. This will act as bedding for the drainage piping.
Why do I need gravel in a French drain?
It is important to place the gravel around the pipe because they will filter any sediment that the geotextile is not able to remove.
Do you need gravel under drain pipe?
Quote from Youtube video: Yeah you got to put stone under the pipe otherwise the pipe when it sinks into the clay. Into the mud i mean you got a water problem so the subsoil gets saturated during the spring and fall the rainy.
Do you backfill French drain?
A French drain is also known as a sub-drain, a perforated pipe designed to pull excessive water from soil and away from areas such as house foundations. Installing a French drain prevents ground water saturation. Although sand will work for back-filling a French drain, it is not as good a choice as gravel.
How much soil should be in the top of a French drain?
Before installing any drain lines, coarse stone or gravel should always be put in the bottom of the trench to a depth of approximately two inches. Once the drain line is installed, coarse stone or gravel should then be put on top of the drain line leaving approximately 3–4 inches for topsoil for the lawn to grow in.
Should I use landscape fabric in French drain?
Non-woven geotextile fabric is the best choice for drainage applications where water flow through (permeability) is the main concern. Non-woven landscape fabric is commonly used in French-drains, drain-fields, and erosion control.
What size gravel is best for a French drain?
1/2 to 3/4 inch
For the best drainage, look for coarse washed rock (gravel) that is screened, with a stone size of 1/2 to 3/4 inch. Smaller rock with fine particles could clog the holes of the drain pipe. Pea stone works, but the smooth stones settle together and don’t move as much water as coarse rock.
How much rock is needed to cover a French drain?
You would need around 0.72 cubic feet of gravel per foot length of French drain for a typical French drain width of 10 inches and a depth of 12 inches if you’re using a 4″ drain pipe. On the other hand, you would need around 0.6 cubic feet of gravel if you’re using a 6″ drain pipe.
How much gravel do I need for a 50 foot French drain?
To calculate gravel needed for a 50′ french drain, multiply the length of the trench by the width and depth. If you plan to lay down 4 inches of gravel, multiply 50 feet x 4 inches = 200 cubic feet.
