A French Drain is a long perforated pipe in the bottom of a trench. The trench runs through the problem drainage area. The trench is filled with gravel or crushed lime stone. The French Drain takes in water any place that water runs into the trench.
1. Water gets to the problem area by falling from the sky.
2. Water gets to the problem area by flowing down hill over the ground.
3. Water gets to the problem area by flowing underground. (Sub-Surface water flow)
Number 3, Sub-Surface water flow is the big consideration. When doing a Drainage Diagnostic, this is the area that is many times missed or not considered by less experienced companies. CMG relies on 21 years of experience. Many Times it is cheaper and more effective to install a French Drain over a Surface Drain. A Surface Drain can’t move as much water as a French Drain, and a Surface Drain can’t Drain away Sub-Surface water. Surface Drains should be installed in areas where the Drainage Problem area is smaller and is not affected by sub-surface water.
French Drains do a great job running along foundations and driveways. A French Drain will keep water away from cement and prevent damage to concrete if water should freeze up against it. A French Drain can keep your foundation Dry.
We just finished a 4 inch Drainage System in Yukon. It was a complicated system to install. It utilized 4 inch French Drain in the flower beds, 12 inch Surface Drains on the side of the house, 6 inch French Drain along the garage foundation with 2 Pop – Up Emitters in the back yard and 3 Curb Fittings in the front. First we installed 4 inch French Drain in the flowerbeds on both sides of the front door. We connected 4 inch solid Drain Pipe into the French Drain and ran them underside walk to the curb. Next we cut the curb with a concrete saw and installed 3 curb outlets for 3 separate French Drains.
Next we installed 4 12 Inch Drain Basins with grates along both sides of the house continuing with Solid Drain Pipe to the Pop-Up Emitters on the back fence. Finally we completed the Drainage System by installing a long run of 6 inch French Drain down the side of the garage foundation. Installing the French Drains in the flower beds was the most difficult and took the most time. Each French Drain took over a ton of crushed limestone to fill the French Drain trench. The Six inch French Drain took even more limestone.
French Drains can utilize several types and sizes of French Drain Pipe. An older type that is not commonly used any more is 4 inch PVC Pipe with large half inch holes drilled in the Pipe. This doesn’t work very well, Because the holes are too large and the number of holes in the French Drain Pipe are too few. Also there is no filter or “Soc” around this particular French Drain Pipe. If it is used in sandy or loose soil the holes will clog and the pipe will fill up with sand. PVC French Drain Pipe should be avoided.
ADS French Drain Pipe is much better, the holes are smaller and much more numerous. It also comes inside a soc that acts as a filter and helps keep sand and debris out of the French Drain Pipe. It works very well.
For Small business and Residential French Drains, Four inch ADS Perf/Soc French Drain pipe is adequate and the most common. It is used for the majority of all French Drains installed. French Drains can be installed using 3 inch ADS Perf/Soc but many times it is too small and can be overwhelmed by a heavy rain or from a bad design. (Too many gutter down spouts connected directly into the French Drain, For Example) Three Inch French Drain Pipe should be avoided if possible.French Drain Compared to Four Inch Pipe. 2. Many times 6 Inch French Drain Pipe is too large for many applications, Such as going under a fence or sidewalk. 3. The trench for a 6 inch French Drain must be much larger than a 4 Inch 4. The amount of gravel or limestone or River Rock used to Cover the 6 inch French Drain is Much larger All things being considered, the performance and longevity of a 6 inch French Drain is well worth it if you are trying to protect something of value to you! If the higher cost and the additional labor and materials are not a problem and 6 inch French Drain pipe is not too big for what you want to do then a 6 inch French Drain would be the best.