Best French Drain System for Clay Soil (Best Design)

Clay soil has the least water percolation rate which makes it difficult to drain the water in lawns and backyards. French drains can offer a great solution for water drainage in clay soil.

But French drain for clay soil comes with slight modifications in its design. You have to perform those modifications to get the best drainage in the clay soil landscape.

Let us find out the best French drain system you can lay for a lawn area that has clay soil. 

Best French Drain System for Clay Soil

French drain installation for clay soil avoids the use of landscape fabric and requires the installation of catch basins at water pooling areas. Instead of landscape fabric, you have to use gravel beneath the perforated pipe and above the perforated pipe to cover it. This will enable better drainage in clay soil, and you can avoid water stagnation on the surface very effectively. 

Let us understand the French drain design for clay soil in detail so that you can devise the best design that lasts longer. 

Design Considerations in French Drain for Clay Soil

French drain installation is pretty much the same concept and design for clay soil except for a few considerations and changes. They are:

• Avoiding Landscape Fabric
• Use of Thick Gravel stones
• Use of Catch Basins
• Deeper Trench with outlet

Avoiding Landscape Fabric

Landscape Fabric is a woven cloth that helps in filtering the water from debris and dust. This can be very useful in other soil types. But in clay soil, this fabric is not an effective solution. 

We know that clay soil has a very soft and nice texture when it is mixed with water. The fine particles in the clay soil obstruct the tiny holes present in the landscape fabric which reduces the percolation of water through it.

So, when you use fabric in the French drain laid for clay soil, you can find it to have very poor water percolation once the soil is saturated with water. This will lead to poor drainage. 

Therefore, when laying the French drain in a clay soil area, you should avoid wrapping landscape fabric around the perforated pipe. 

Use of Thick Gravel Stones

If we are avoiding the use of fabric, then how to filter the percolating water? This is where the use of gravel stones comes into play. 

In usual French drain designs, we will fill the gravel only beneath the perforated pipe and cover the pipe with landscape fabric. 

But for clay soil conditions, we will be covering the pipe completely with large thick gravel stones that will act as a filter for the percolating water. 

After digging the trench, fill a layer of gravel for an inch height and place the perforated pipe over it. Then again fill the trench with gravel covering the pipe. This will provide you with better drainage and faster percolation. 

Use of Catch Basins

French drains with catch basins last longer and perform well in any soil conditions. But with clay soil, you have to use more catch basins at prime locations to enhance faster percolation.

Catch basins aid in the capillary action that results in faster percolation of water into the soil. Since clay soil is very fine and becomes a thick paste when mixed with water, these catch basins help in the free movement of water into the soil.

First, you have to find out the areas where water stagnates and pools around. Then you have to dig a square hole to fit the catch basin and the grate in all those water pooling areas.

Connect these catch basins to a main French drain line that leads to an outlet. You have to use proper pipe couplers and connectors for effective connectivity.

Deeper Trench with an outlet

Normally French drains are dug 18 inches deep and 12 inches wide. But for a clay soil system, you can go deeper than 18 inches for two reasons:

• You can get a different soil system after a particular depth
• Reduces water stagnation on the surface

Therefore, when you are designing a French drain for clay soil, you should go deeper than 18 inches and fill it with gravel.

Usually, French drains need no outlet. But a French drain designed for clay soil must have an outlet. Because the chances of water percolating and seeping below the clay soil are very less. 

Therefore, with an outlet, the water travels through the perforated pipe and exits away from your land. When you are designing a French drain for clay soil, install an outlet to enable better drainage. 

These are the things you should consider before designing and installing a French drain for clay soil. If you include all these aspects, it will be the best French drain system that lasts longer no matter how large the downpour occurs.

Is French drain good for Clay Soil?

A French drain is an excellent system to prevent water stagnation in your lawn, backyard, and around your house. With proper design, you can get the best drainage with a French drain.

Clay soil doesn’t allow water to percolate easily. But a French drain enables higher percolation and transfers the stagnating water out of your property. 

Excess water stagnating in the clay soil will take a very long time to dry and you cannot use the area until then. 

So, if you want to improve drainage in your clay soil property, a French drain is a highly effective and efficient way to do it. Also, it enables you to combat heavy rainfall on clay soil with faster drainage.

Read Also: French Drain For Septic Tank

Conclusion

The French drain system is a must for every property to avoid water stagnation. Particularly if you have clay soil on your property, you should lay a French drain with the above-mentioned specifications. With the right French drain design, you can have the most effective drainage which makes it the best drainage system for clay soil.