Backfill for french drain in clay soil
Backfill for french drain in clay soil
(OP)
I am building a french drain in a high clay soil at my house. I am planning on backfilling the trench with sand to filter the clay and using a drain sleeve filter on the perforated drainage pipe.
I am able to get a ASTM D6707 drain sleeve filter with an AOS of 0.6mm. What kind of sand should I use? I can easily get mason sand, general purpose sand, and play sand.
Thanks,
Fred
I am able to get a ASTM D6707 drain sleeve filter with an AOS of 0.6mm. What kind of sand should I use? I can easily get mason sand, general purpose sand, and play sand.
Thanks,
Fred





RE: Backfill for french drain in clay soil
RE: Backfill for french drain in clay soil
RE: Backfill for french drain in clay soil
RE: Backfill for french drain in clay soil
Thanks,
Fred
RE: Backfill for french drain in clay soil
the idea with the graded filter is to place the gravel next to the pipe then the sand around the gravel. This means putting some sand in the bottom of the trench then some gravel then the pipe followed by some gravel and lastly filling the remainder of the trench with sand. However, you need to be carefull to keep the sand between the gravel and the clay walls in all cases. Also, the gravel must be properly graded to keep the sand from washing into the voids in the gravel.
Mixing the gravel with the sand will not change the permeability of the sand, so that will not work.
Unless you have or expect a lot of water flow, you probably do not need the gravel. If you post some information about the problem you are trying to fix with the drain, we can offer some advise.
RE: Backfill for french drain in clay soil
The same negative comment goes for lining a trench with fabric and using gravel inside. A labor intensive thing which easily can be goofed up. Take it from this old guy, never have I had a job go bad using concrete sand directly against the pipe, including the old Armco "wrinkled tin" subdrain pipes with 3/16 " holes. The first such job (in clay) was done in 1955 and it still works fine.
RE: Backfill for french drain in clay soil
RE: Backfill for french drain in clay soil
RE: Backfill for french drain in clay soil
Let's take the case of providing a cut off drain for a failing slope. You want to set the pipe as deep as possible, say 15 feet. No way should any one go in that trench. So you dig the trench, follow behind the machine by rolling in the plastic slotted pipe and dump in that sand quickly. It works and is safe.