French drain liner

padraig.od

Hi,

I am putting in a 20m french drain across my lawn. I've read in a number of places that I should line the trench with a permeable landscape fabric to stop silt and fine dirt from filling up the drainage pipe.

Can anyone recommend a fabric? I've done some looking around and there are massive difference in prices between products. My local garden centre is selling high quality stuff for €1 per foot for 1.5m wide stuff. They have cheaper material for about half of that price. Aldi are currently selling their own brand material for €6 for 10x1m. For the job I am looking to do would you expect there to be much difference between the products?

Patrick

_Brian

It’s really not necessary

recedite

The proper stuff is a fleece material, but I've only seen it in massive rolls.
If you put 20mm pebble or pea gravel around the pipe, and then put sand around that, the sand will keep the topsoil out. More fiddly, but no need for the liner.

padraig.od

OK thanks for the information. I was planning on using washed 2 inch rock around the pipe, without any sand. Would the sand not work its way into pipe if it was washed through?

Lumen

I don't know what your soil is like, but I can sculpt mine there's so much clay in it. With this sort of soil there isn't loose material moving through it, at least below the top couple of inches.

As evidence, I dug up an old land drain pipe a couple of weeks ago that was unprotected by anything, and it was empty inside.

If the drain is absolutely critical to something structural like your house foundations, by all means go the whole hog, but for simple garden drainage I doubt it's necessary.

recedite

padraig.od wrote: »

Would the sand not work its way into pipe if it was washed through?

Its all about grading down gradually. If using 2" stone, you'd have to put some finer stone or gravel on top of that before the sand. The sand then stops the even finer soil percolating through.

blackbox

You'd need strong fabric for under gravel on a driveway but I'd say the Aldi stuff should be perfect for your application.

padraig.od

The drain isn't critical for house foundations. I have a lot of standing water in a section of my lawn and I've dug the drain to move the water elsewhere. I'll be using a buried perforated 4 inch pipe to collect the water. Without the fabric and rock I would be concerned with the pipe filling with silt from underneath and the drain becoming blocked. I've dug the trench myself and given the length and depth of it I want to ensure I don't have to dig it out again to clean it.

aw

padraig.od wrote:

The drain isn't critical for house foundations. I have a lot of standing water in a section of my lawn and I've dug the drain to move the water elsewhere. I'll be using a buried perforated 4 inch pipe to collect the water. Without the fabric and rock I would be concerned with the pipe filling with silt from underneath and the drain becoming blocked. I've dug the trench myself and given the length and depth of it I want to ensure I don't have to dig it out again to clean it.

For the small amount of money involved I'd put it in, even if just for your own peace of mind.
Have you held and felt a difference in the two fabrics?
If not, go cheaper.
If even a sight difference, I'd go for the more expensive one. At least then you've done the best you can and it's not big money, especially if it's going to last you 10,15,20 years.

_Brian

Literally thousands and thousands or meters of drains are installed every year with no fabric on farms.

I have French drains running fine after 30 years. With just 4”perforated pipe surrounded with 2” clean stone.

The thing I can’t understand with the idea of fabric, if there is so much loose material floating about in the water the fabric would block quicker than any problem on the pipe as it’s a much finer mesh.

As for sand I’ve literally never ever seen this done.


It’s important to understand where the water is coming from and what sort of soil you have.
If your draining an underground spring etc then it’s importsnt to get your drainage pipe right to the source of water.
If your draining surface water and on clay soils then it’s harder and the stone in the drain needs to come right up near the sorface or the clay will literally seal the surface and the water won’t get down to it.
Of course sand into clay soils is a big no no as they mix to form a harder denser layer that’s a total disaster.

my3cents

OP, I'd started to write chapter and verse on this but then I remembered reading this a while back https://www.teagasc.ie/media/website/publications/2013/Land-Drainage-Manual.pdf .

Lumen

my3cents wrote: »

OP, I'd started to write chapter and verse on this but then I remembered reading this a while back https://www.teagasc.ie/media/website/publications/2013/Land-Drainage-Manual.pdf .

Fascinating.

"As our soils were formed by deposits from melting glacial ice, the heavier coarser particles (sands and gravels) tended to be dropped first followed by the light fine particles (silts and clays). As a result the poorest subsoil can be close to the surface while more permeable layers can be found underneath."

Has anyone tried digging through this clay layer? I went down about 65cm recently and was still in heavy clay.

padraig.od

my3cents wrote: »

OP, I'd started to write chapter and verse on this but then I remembered reading this a while back https://www.teagasc.ie/media/website/publications/2013/Land-Drainage-Manual.pdf .

Wow, thanks for this I will give it a read and apply it to my own situation.

padraig.od

_Brian wrote: »

Literally thousands and thousands or meters of drains are installed every year with no fabric on farms.

I have French drains running fine after 30 years. With just 4”perforated pipe surrounded with 2” clean stone.

The thing I can’t understand with the idea of fabric, if there is so much loose material floating about in the water the fabric would block quicker than any problem on the pipe as it’s a much finer mesh.

As for sand I’ve literally never ever seen this done.


It’s important to understand where the water is coming from and what sort of soil you have.
If your draining an underground spring etc then it’s importsnt to get your drainage pipe right to the source of water.
If your draining surface water and on clay soils then it’s harder and the stone in the drain needs to come right up near the sorface or the clay will literally seal the surface and the water won’t get down to it.
Of course sand into clay soils is a big no no as they mix to form a harder denser layer that’s a total disaster.

I'm draining surface water from a couple of spots in the lawn. The water has been ponding in the same places since we did the lawns. The drain has been dug and is open currently. Patches of the lawn are still pretty boggy though.

I think the idea of the membrane is to stop smaller material from getting into the pipe and blocking it.

recedite

_Brian wrote: »

The thing I can’t understand with the idea of fabric, if there is so much loose material floating about in the water the fabric would block quicker than any problem on the pipe as it’s a much finer mesh.

Its the surface area. If the fleece is around the stone (not the pipe) its surface area is massive compared to that of the pipe itself, which stays clean.

_Brian wrote: »

Of course sand into clay soils is a big no no as they mix to form a harder denser layer that’s a total disaster.

Maybe that's cement you are thinking of, not clay.https://www.gardenmyths.com/sand-and-clay-dont-make-concrete/
Golf courses use sand all the time as a top dressing to improve drainage.
In a damp climate, and using normal sharp sand, sand is good.

recedite

Lumen wrote: »

Fascinating.

"As our soils were formed by deposits from melting glacial ice, the heavier coarser particles (sands and gravels) tended to be dropped first followed by the light fine particles (silts and clays). As a result the poorest subsoil can be close to the surface while more permeable layers can be found underneath."

Has anyone tried digging through this clay layer? I went down about 65cm recently and was still in heavy clay.

Only applies if you live on top of a quarry or a drumlin.