Recently we installed a French Drain inside the court yard of a rest home in Norman. We had several interesting challenges to overcome that were not typical for a French Drain Installation. The court yard was in the center of the home and was a secure area for the patrons. We had to put down painters tarps to run our wheel barrows over. We took out 44 loads of dirt and brought in 52 loads of Crushed one inch lime stone for the French Drain. Each trip was over a hundred yards from the trailer in the parking lot, in the front door, down the hall, making two turns along the way. Each time we had to be escorted by security. Needless to say, the installation of this particular drainage system took a while.In the above picture, the French Drain runs along the low area crossing all the areas where water would stand each time it rained.
When a French Drain is installed, a big mistake that is made by many people is to cover up the gravel with dirt. This is a big mistake. Basically it is ” Putting the cork back in the bottle.” If the French Drain is in full sun and has a type of grass surrounding it that spreads on its own such a ” Tift” or “Bermuda” , Grass will grow over it and the French Drain will eventually disappear. Grass covering a French Drain is a good thing if it grows across the drain without adding dirt. The Grass thatch acts a water filter preventing clogging and extending the life of the Drainage System.
When a French Drain is in Full Shade, or the surrounding grass will not spread on its own, such as with Fescue, other steps must be taken. One option is to just leave it alone. If you don’t mind how it looks, it will drain a large amount of water for many years. Many times a French Drain can be a landscaping focal point. They can be dressed up with all kinds of Rocks and Stones and Plants.
Just what is a “French Drain?” Many times people incorrectly
- A French Drain can protect your foundation!
use the phrase, “French Drain,” to apply to many different types of Drains that could be used in a Drainage System. The term is widely used and many times incorrectly connected to “Surface Drains,” or “Channel Drains.”
A Surface Drain has a grate that sits on top of a basin. The basin is underground. A Drain Pipe is connected underground to an outlet on the Drain Basin. Storm-Water Drains through the grate into the Drain Basin. Once in the Drain Basin, water travels out of the basin through a Drain Pipe. The Storm-Water continues downhill in an underground Drain Pipe to an exit point.
THIS IS NOT A FRENCH DRAIN!
A French Drain is completely different from a Surface Drain. A basic French Drain consists of a Perforated Drain Pipe in the bottom of a trench. The Drain Pipe should have a neoprene sock around the Perforated Drain Pipe. This is to ensure that the Drain Pipe does not become clogged.
The dirt that was taken out to make the trench is hauled away. It is replaced by some type of small stone or gravel depending on what is desired or available. I prefer crushed 1 inch lime stone. It is the most economical option in my area. Pea Gravel or some other type of small stone can work just as well. The lime-stone or gravel is placed in the trench on top of the perforated Drain Pipe and filled all the way to the surface (ground level). In some cases where the French Drain needs to be deep or is being placed in sandy soil, a special trench liner must be placed in the trench before the perforated Drain Pipe or the Gravel are installed. This helps maintain the integrity of the trench over time. It also increases the cost of the French Drain and the amount of time to install it. I install a trench liner in a French Drain about 20% of the time. Most of the time a liner in not needed.
- French Drain March 2011