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French Drain Installation

French drains are an effective way of draining excess water from your house or a tract of land. Knowing how to install one, you can effectively divert water to other areas and save your home basement from moisture-related problems.
Gardenerdy Staff
Last Updated: May 30, 2018
Paris Sewer
Of all the French things, you might not have heard about the French drain. They were invented by Henry French, who lived in Concord, Massachusetts, in the 19th century. They are really a very simple and ingenious method of draining out water, from clogged areas.
Now, in its modern form, the French drain style has been modified and most of the errors of the old style have been removed. It can effectively solve your local water clogging problems.
How Does it Work?
Overhead view of gravel 2
This type of drain, in crude form is a sloping ground trench, filled with gravel, such that it directs water away from clogged areas, as water percolates through it. Modern drains of this type, have a perforated pipe, built into the ditches, covered with soil and sods.
These drains work on gravity. The gradual slope helps in draining water away. Building one, is an established way of saving building foundations from water penetration problems.
Here, ideas, methods, precautions, advantages and disadvantages of installing such a drain, are presented. First, note down the tools you will need to dig and install one.
Installation Tools
Following are the tools, that you will need:
  • Tape
  • Landscape Fabric
  • Sand
  • Gravel
  • Sod
  • String
  • Two Stakes
  • Spade
For digging, you may use other mechanized tools like 'Trenchers'.
Metal Shovel
Wooden stakes on grass
Installation Instructions of French Drain
Step 1: Scouting for a water rerouting spot
Fine beach sand in the summer sun
The first thing to do is to determine which spot you are going to drain the excess water to. It needs to be a spot with sandy soil, through which the water can seep down easily.
Take help from a surveyor to determine the right spot for the drain outlet. This may save you from litigation, in case, you unknowingly damage somebody's property by draining water there. After determining the spot, plan the path for the drainage trench.
Step 2: Get the Digging Go-ahead
Check with the local authorities for any underground cables that might be damaged because of falling on your digging route.
Nowadays, there is a facility available called 'Dig Safe Phone number', provided by civic authorities. There, you can check out for underground installations that might be damaged and get a go ahead from them. It is absolutely necessary that you do so.
Step 3: Plot Trench Line Route
Next, find and plan a path for the drain to run down. For that, you must consider the topology of the area around the house. French drains work under gravity. That is, it's necessary that they have a slope. Otherwise, water will not drain out easily. So, find a path, along the sloping area of the property.
If a pronounced slope does not exist, you have to create your own. This can be done by designing a sloped trench of a specific grade. A grade is measured in percentage. For example, a grade of 1% would be a drop in altitude of 1 foot, every 100 feet. A grade of 1% is recommended.
Step 4: Start Digging and Maintain Grade
So accordingly, mark the path of your drain and start digging the trench. The width of the drain will be decided by the magnitude of the moisture problem you are facing. If the amount of water clogging is very high, then dig a wide trench. If the problem is low, dig one with a smaller width.
Measure depth of the drain at regular intervals so that the proper grade of slope is maintained. Fix two stakes at the beginning and end of the trench path. Tie a string that connects the two stakes, along the ground and make sure that it is taut. As you go on digging, check the depth, with reference to this string.
Step 5: Put the Landscape Fabric and Gravel In
Black landscape fabric
After digging, cover the trench with landscape fabric. Pour the gravel into the trench. Spread it over the length of the trench. Cover it again with landscape fabric and your drain trench is ready.
Heap of sod rolls for installing new lawn, unrolling grass
Cover the rest of the trench with soil and put sod over it. From a landscaping point of view, the sods cover the drain effectively and the beauty of your lawn need not be ruined. With the completion of this step, your construction is over and done with.
A French drain is a simple and straightforward solution to the water logging problems near your house.