1 of anything is small. How big is 1cm?

I missed that class.

Gary,
Maybe a little smaller than a dime (.10). Thanks.

The pipe will only have 2 holes on the top running along the pipe. Kinda like snake bites. Here's an example:

Here is a link that might be useful: example of pipe

I installed drainage pipe like that last year and put down limestone, then pipe, then back-filled with limestone then filled with soil, tamped the soil, then added a bit more soil. Seeded and as of early March after a long winter, hardly any settling and looks great. May have to add a bit more soil in a few small areas, but thats all. Limestone is my recommendation.

Thanks, pt.

One more question: did it work? solve your problem?

Why is your lawn soggy? I'm guessing it is in a low spot. In theory all you should have to do is add soil to the low spot OR lower the area around the soggy soil. Which choice is correct depends on general drainage away from your house and permanent structures.

Have you considered sand? Like to the surface? A French drain is usually not much of a French drain anymore if the top is not open to the surface. If the soil was porous enough for water to move sideways sub-surface to the drain capped with soil, you probably would not even need a drain line.

Also, pea gravel cannot compact. It would have to be fractured first. It's virtually impact-proof. Crushed stone would be closer to something that compacts.

So "1 cm" - that's 1/100 of a meter. That's a decent size stone too.

The page below has a bunch of information that you might pick and choose from if anything looks related to what you are working on.

Here is a link that might be useful: Drainage advice for French drains, drainage and some soil information

I installed one last year and had about 3in. of soil over the landscape fabric that wrapped around the pea gravel & pipe. The grass over that area (the highest point of the french drain) was a little bare compared to other areas where the pipe was deeper. I can't say for sure if the shallow soil depth caused the bareness or if drainage in that area was the cause, since that was where most of the water would sit. If you can go the deeper the better.
Also from what I've research before installing the french drain, you should turn the holes down. This has something to do w/ allowing the ground to soak up first til it's saturated before sending it up the pipe. I think it also makes it harder for pipe to get clogged. Check out this link, it's extremely helpful.

http://www.easydigging.com/Drainage/installation_french_drain.html

I dug a French drain across my turf on a slope. I encased the slotted plastic pipe in a fabric sleeve before burying. The sleeve seemes to hold the topsoil better on the surface and the grass roots seemed to anchor themselves into the fabric. Not even a trace of evidence it is there. :)

The perforation on drain pipes should be at the bottom of the pipe when layed in the ground. The size of gravel won't matter as far as concern for the hole size when the holes face down as they should. The collecting water should make its way through the gravel to the bottom of the trench. As it rises in the trench, it will then make its way into the drain pipe via those holes that should be on the bottom, and then the water will follow the track of the pipe. Most likely you drain pipe will have two series of holes. When you install the pipe, simply lay those holes towards the bottom but in a way that both lines of holes are slightly offset from the center and are equally accessing the BOTTOM of the trench technically the gravel in the bottom of the trench. If still you are concerned about gravel getting into the drain, you can wrap the drain pipe with poly mesh netting. Those holes must be to the bottom of the drain in order for the drain to function properly. Also make sure you obtain the proper slope for your drain pipe when you install it. Good luck.

All good advice, but this thread is SEVEN YEARS OLD