Another retaining wall ?

[ALBALD1]

after reading a little about french drains, it seems too simple. just put gravel in a ditch then a perforated pipe wrapped in fabric & more gravel. No dirt on top, just gravel. Does this sound right?

[twstanley]

That's it, they work great. Make sure you have the recommended slope in the ditch so the water will move where you want it to, not just sit in the pipe and stagnate.

At the end of the pipe you can have an outlet at grade or dig a gravel filled sump for the water to go into to drain down into the soil....

[ALBALD1]

How do you determine the depth & pipesize?

[Pat]

Unless you have an enormous flow of water, you will get by fine with 4 inch black plastic perforated flexible drain line that comes in rolls at the big box stores. You can buy a "sock" (also in long rolls) made to fit over the drain pipe and prevent the perforations from being plugged with fines. This pipe is also available in unperforated if you need to lead the water away from the area of the French drain.

The BEST constructon detail is:L

1. put down geotextile
2. put down 3-4 inches or more of gravel
3. place your sock covered drain pile on the gravel
4. cover with more gravel
5. pull the "extra" geotextile up and over from both sides to cover the gravel
6. at this point I "pin" the cloth together with galvanized nails every foot or two.
7. cover with at least enough gravel to hide the cloth.

You don't have to do all of this to make a good working French drain but the above will help ensure that it CONTINUES to work well in the future by avoiding fines infiltrating the gravel bed and plugging it and or the drain pipe.

Use washed "SEPTIC" gravel as it has no fines to plug up the drain action. Ground up recycled tires are a good gravel substitute and are much much easier to shovel than gravel if you are doing this manually, sans FEL.

If you really want to be proactive, install a cleanout/flush port, a provision to flush the inside of the drain pipe with water from a hose.

I have installed several French drains and have NEVER had a failure or reduction in function. My most recent French drain installations are for my walkout basement. (See Oklahoma farmhouse thread in house building)

My walkout basement floor is from 1-4 feet below the ground water level most of the time and is protected by French drains which have been flowing continuously since installed over two years ago. Floor is quite dry.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]