30. French Drain

Hidden drain burrito under Kebony.

We are installing Kebony wood walkways to connect our new patio to the pool. The only problem is surface water drainage. The solution: a French drain.

What is a French drain?

From the Spruce:

A French drain is a simple trench dug in the ground in the most problematic areas of the yard. The trench is filled with a perforated pipe wrapped in water-permeable fabric, and the pipe is covered with several layers of stone or gravel.

French drain systems work because gravity causes the water to flow downhill, and water will always follow the path of least resistance, so it is naturally drawn down through the stones into the hollow pipe where the water can flow freely on a downward slope

Drainage below Kebony

Our Kebony decking instructions specify for drainage with a directly over ground installation. Here is an excerpt from the manual:

We will be installing our Kebony flush with the grade on both sides, making this drainage issue even more critical.

We have about a 30” change in level from the top of our new patio to the pool deck, so as long as water has a way to get water out from under the wood walkway, drainage is not a problem.

French Drain Construction

Here are the steps I took to create our French Drain.

(1) Dig the trench:

(2) Cover with filter fabric:

(3) Fill with 1 to 1 1/2” round rock:

(4) Add perforated pipe (sloped to drain with holes on the bottom):

(5) Test the drainage:

(6) Cap the ends (cover w/filter fabric and rocks):

(7) Cover the pipe with more rocks:

(8) Wrap the filter fabric over the rocks:

(9) Make a tidy burrito:

(10) Replace soil on top of the drain:

All done!

My next step is to install the Kebony; we have a few other projects higher on the priority list, but soon!