French Drain

[at_obuk]

I have a water drainage problem. Water drains from the concrete pad in front of the garage and off the driveway into the yard. While this isn't that bad on normal rainy days it can get pretty soggy on heavy rain days or if it rains day after day.
Anyway heard about french drains. Know how they work but never learned how they are made.
Me and me Kobuta want to do it!!!!!
Anyone out there who can help with the how, like how deep what kinda stone etc etc???

Thanks

Eric P.

 

[siphoxolo]

Hi

I have just built a huge one for our septic tank overflow. They work very well. I dug about a 15 m x 2m x 1.5 m deep trench. ( This was all done by hand as I dont have a backhoe). I then drove in 8 x 1.5m3 loads of building rubble. Sizes ranged from 1/2 to full bricks. Dumped that load in and covered it with old plastic sheeting and shovelled some topsoil on top. I have been told that you can use old tyres - by placing the sidewalls as close togeather as possible. This forms a hollow in the middle for the water to drain away. The tyres will never break down and it should work well for rain water.

The brick drain lasts us about 10 or so years. Our soil is very sandy ( Beach sand at lower levels)

Hope that answers your ques.

Cheers

Siphoxolo

 

[Knight9]

Check these out:

Building French Drains

French Drains

French Drains 2


There are some more if you search for "French Drain" that were not as long (though may contain useful information).

Good Luck,
Kevin

 

[Darren]

The depth depends on the length of the run until you can find a low point for discharge. Without being able to get rid of the water, the drain will be useless. Since you're trying to remove the surface water, there's some other considerations. The last question is how high is the water table in that area? That could complicate things.

Other than that you dig the trench, line it with geotextile to prevent soil infiltration, lay in the perforated pipe (perfs down), backfill with pea gravel over the pipe and in your case higher since you want to pick up the surface water. fold the geotextile over top of the pea gravel, and then backfill the rest of the trench to a few inches of the top with free draining sand. Finish backfilling the last few inches of the trench with soil.

I put one in a few years ago and it removes water so efficiently that in hot, dry weather the grass over the drain actually browns out because of the lack of water. The rest of the yard in that area stays green. It still beats the water that used to pool by the house.

 

[CTyler]

My case is a little different than yours but this is the basics of it.

I built mine for the down spouts off my house. Basicaly dug a 50' trench 2' wide and 2' deep where the perf pile was laid. Used 4" black flexible sewer pipe from the spout out away from the house 10'. Then connected the perf pipe, same stuff but perferated all around. Put several inches of pea gravel, called road gravel aound here, in the bottom. Then lay out the pipe and cover with more gravel. Then cover the last 8" with dirt and planted grass.

 

[ByronBob]

With a clay base under the topsoil you might not need fabric but if the soil is loose then get some. I would say a 12-16" depth is necessary out to daylight but it depends how far you need to run the drain. Crush stone will work but pea gravel is rounder and will allow for more water volume to move it. the drain will want to be pitched to let gravity help you. The links are very useful so I'd read up on them.

 

[Darren]

The problem is that most soils aren't pure clays. They're a mixture of clay, silt and sand. Not using fabric in a supposed clay soil, but which still contains silt or sand, may mean the difference in the drain blocking in 30 or 40 years vs. not in your lifetime (with the fabric) or never. The more silt and sand in the soil, the faster the drain will be blocked without the fabric.

A quick way to check the soil composition is to take some of the subsurface soil and put it into a quart jar of water and shake it up good. The sand will settle out first followed by the silt and last the clay which may not completely settle out for days. If you have lots of stuff settling after a few minutes, the fabric is a good idea.

 

[Degree]

Ive built only one french drain and it was very simple yet worked so well. I dug a trench about 6 inches and then dumped about 10 bags of pebbles. I covered it up with sod and topsoil and it works really well.

 

[Darren]

Initially it will work. It takes time for the soil to infiltrate the gravel and fill the voids. Once that happens, you no longer have a drain. How long that will take, is unknown. That it will, is virtually certain like the first poster who said the drains usually last ten years. I'd bet your's will last longer since I suspect you don't have mostly silt or sandy soil. If I'm wrong on your soil, it will block sooner. But at least you don't have much involved in the construction. For those putting in longer and deeper drains, it'll save a lot of aggravation later if it's done correctly the first time. If they don't think they'll own the property 20 or more years down the road, some other owner will get stuck.

Using fabric is one of those things you rarely see contractors do unless they're working to a spec that requires it. Why put in something that costs money and the new owner can't see? Besides the contractor will be long gone before the problems show up.

 

[Junkman]

I agree with Darren on this. I just installed a drain this week end and used the fabric. I purchased 3 rolls of it at Lowe's on the sale table for under $20 each. Each roll is 48" X 300'. What I don't understand is why it was on the sale table. I checked a few weeks later and they were still carrying it in the department, but for more money. To me, the landscape fabric was so cheap, that I used a double layer just in case it should get a hole in it. Cheap at twice the price to know that you only have to do the construction once.