French Drain Questions

[vizmark]

In an attempt to stop any ground water from finding its way under my slab and down spout water from pooling, I'm installing a french drain. My plan is to run 2 3" drain pipes. One pipe will be solid for the down spouts and the other will be perforated for ground water collection. This all will be placed into a 12" x 12" ditch covered by #3 drain rock.

We get about 60" of rainfall a year so I feel having a dedicated down spout pipe is important.

Am I over thinking this or is this a reasonable plan?

 

[theoldwizard1]

Check out My French Drain and Dry Well Project

The most important thing is where are you sending the water ? In my case I have a dry well which is filled with 3/4" crushed limestone. It still occasionally overflows (4" vertical pipe with grate at ground level). If you are hoping the drain will dissipate the water, how long will it be and what kind of soil do you have ? (Clay is BAD.)

If you are hoping your 12x12 ditch will dissipate the water I don't think it will be big enough, especially if you plan on covering it with sod.

Your ditch needs to be lined with construction grade landscape cloth BEFORE you place the rock in to prevent the surrounding dirt from infiltrating and eventually clogging the space between the rock.

If you are going to put sod on top, dig it down 24", fill with 12" of rock, then fold in the landscape cloth and place dirt and sod on top.

 

[pablo94sc]

Bigger is better. You can usually call the local geology dept at a local university or the government to find out soil types in your area, but the best option is to do a percolation test to see how your soil drains. Dry wells can be simply deep holes lined with fabric and stone, and you can put them every so many feet under the drain pipe to aid in drainage. Lots of good articles on it, so google away.

 

[vizmark]

The soil is clay and doesn't perk well. The two 3" pipes will merg into a solid 4" and go over a bank. There will be no sod over the ditch. I'm going to cover the ditch with 3 foot fabric and more rock to make a 3' decorative walk way( which will very rarely be used).

 

[matt_i]

I think 3" dia is too small for a gulley-washer rain. Especially in corrugated pipe with a lot of internal friction (you didn't mention the distance) Personally I would go to at least 4" pipe for the downspout, and then to 6" pipe, at the merge. I also would not install a perf pipe without the silt-sock to keep it from filling solid with clay fines in a couple of years.

 

[theoldwizard1]

The soil is clay and doesn't perk well. The two 3" pipes will merg into a solid 4" and go over a bank. There will be no sod over the ditch. I'm going to cover the ditch with 3 foot fabric and more rock to make a 3' decorative walk way( which will very rarely be used).

You never mention the length of this ditch ! 3' and it is not going to work. 10' maybe, but it had better be 24" wide and 24" deep. 20', you might get away with a 12"x12", but I would want it deeper and wider.

Make sure the ditch is pitched away from the water source.

The ditch need to LINED with landscape cloth to keep the fine dirt (clay is actually very, very fine dirt), from infiltrating. and clogging the space between your rock.

 

[brownbagg]

its best to run to daylight, also put sand or gravel around your pipe. The pipe going need a sock too