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French Drain Sediment Fabric Recommendations / Choices

Posted by uvascanyon (My Page) on
Tue, Sep 27, 11 at 3:25

I am near the completion stages of improving upon an existing drain system, and while I've read about surrounding the rocks completely with a fabric to keep-out sediment, I'm curious if there might be a recommended material to use.

While the vast majority of what I read said to do this (use such a fabric), I did read one opinion, maybe two, that said that these just get clogged and prevent the flow of water downward, defeating the drain's purpose. Not sure how true that is, but figured that it would be prudent to ask what is the desirable fabric to get...

I saw a fabric in the plumbing section of the hardware store which seems just for this purpose, to block-out sediment. Two choices, 2' and 3' wide, I think both 300' feet long. Much more than I need for this application, which is fine I suppose...

I had read that just "normal" landscaping fabric is fine too. The kind of stuff used to keep-out weeds...

Any thoughts or recommendations?

Oh, I also heard about the socks that go over the inlet pipes, in conjuction to the mesh around the rocks. Maybe it was that clogs-up, according to some, not the fabric surrounding the rocks...

Thanks for any input you might have.


Follow-Up Postings:

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RE: French Drain Sediment Fabric Recommendations / Choices

I just used the appropriate weeping tile with the fabric sleeve already on it. Convenient, easy and have never had a problem with clogging up. Perhaps some people may have problems if they skimped on the appropriate sized rocks, either in the bed of the trench or on top of the drain itself?


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RE: French Drain Sediment Fabric Recommendations / Choices

I would stay away from fabric in direct contact with the pipe. Other than that it won't much matter.

Where a proper use of french drains lowers the water table in saturated soil, only a trickle of water is needed to achieve the desired benefit. Almost any reasonable installation will work for an almost unlimited time, whether fabrics is used or not.

On the other hand, where french drains are used as a solution for a surface water problem, they will all have a limited life span. The rate of flow to produce the desired results is often a hundred times that of de-watering a saturated soil. Proper use of fabric may extend the life of the drain, but in the end they all fail to provide the intended benefit. So even here, fabric use is of minor importance.


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RE: French Drain Sediment Fabric Recommendations / Choices

Not all soil structures are created equal and either are geo-textile fabrics.
I usually depend on the geo-technical soils report to inform me of the type of fabric to use.
If you don't have a geo-tech report then you have to rely on your own site analysis and research.
Here is a good link to start your research .
http://www.tencate.com/TenCate/Geosynthetics/documents/Tech Notes/TN_filter.PDF


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RE: French Drain Sediment Fabric Recommendations / Choices

You all are awesome! Thank you so much. Makes much sense too.

I dug the trench by hand, about an hour after work for the past couple of weeks. I can shoot water from the hose inside for 10 minutes, and the level still doesn't quite reach the pick-up or inlets, or at least where the holed-pipe will be located... I'm using an ABS pipe, and making the holes myself, and then of course turning the holes downward.

Someone earlier mentioned rocks, and if I read or understood correctly, there should be two rock types or sizes (one in the bed of the trench, versus on top? If so, I had not heard of that in my readings...

Thanks again everyone.


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RE: French Drain Sediment Fabric Recommendations / Choices

I'm not an expert, but my understanding is that the larger the rock or stone or gravel, the better the water percolation rates.
I have heard of people who used coarse sand and pea gravel - doubt that that would last very long.
We laid a rock bed beneath the sleeved weeping tile, then buried it another 5 inches deep using 1 1/2" - 2" rock. For aesthetic reasons, the front yard drain was brought up to grade using medium sized river rock and decorative blue stone. For the other french drain in the back, once the tile was buried under the 5 inches of 2" rock, we laid landscape fabric on top of that, then filled to grade with soil and plants/sod.


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RE: French Drain Sediment Fabric Recommendations / Choices

I have said this before and at the risk of boring even myself: drainage is totally site specific.Any of the suggestions above are working blind and your latest post suggests that you don't even know the basics so you are blind too. It is so easy to create the opposite effect to the one you envisage as far as drainage is concerned so tread carefully.


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RE: French Drain Sediment Fabric Recommendations / Choices

Thank you everyone for your input. I recently learned that one should use typical landscaping fabric for this application.

There are two such drains here on the land, so I was told, I just don't know what type of fabric was used, if at all. I do know that they have worked well due to the puddling demarcation I see pre / post trench. So, the site is conducive to such... Thanks again.


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RE: French Drain Sediment Fabric Recommendations / Choices

Correction - should NOT use typical landscaping fabric...


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RE: French Drain Sediment Fabric Recommendations / Choices

Using french drains for underground seepage is fine. They are used to go behind retaining walls. They also work well for seepage in around structures to prevent undermining and loss of soil stability. (For this they should have a moisture barrier on the down hill side.)
Using french drains for surface drainage is a very poor idea. First off rock is placed around the pipe to allow for fast drainage. Then fabric is placed around it, which limits flow. Over time the fabric clogs so the drain has no function at all.
Here is a link to one style of trench drain.

I think somewhere in time it may have been suggested to use trench drains, which are entirely different, and people misinterpret it as french drains.
For surface drainage regrading is the best. Trench drains or area drains would be my next choice.

Here is a link that might be useful: Landscape Drainage


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RE: French Drain Sediment Fabric Recommendations / Choices

The link posted by deviant-deziner has been changed. Use the new link below to download the PDF document from TenCate Geosynthetics Division's "Knowledge Base."

READ THIS BEFORE YOU USE FILTER FABRIC!

There is an enormous amount of dead-wrong information on this subject being posted and followed.

-- Paul

Here is a link that might be useful: TenCate


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