French drain which chippings ?

[Loz]

Hi,

 

Dug trench for French drain in clay where flowerbeds are, was about to order the chippings/gravel and have totally confused myself on material and size, the suppliers been using seem to have only limestone chippings and been reading on some posts that this is not suitable as pourous and can create deposits over time, another supplier has decorative gravel - on all the sites with limestone chippings they do say suitable for drainage but on sites on french drains say not to use limestone - would the second link be good- is that the right size - was going to line trench with geo textile fabric and also the pipe, only wanted to go for one type of aggregate if possible,

 

Any advice greatly appreciated,

 

Lawrence

[Loz]

6 minutes ago, Loz said:

Hi,

 

Dug trench for French drain in clay where flowerbeds are, was about to order the chippings/gravel and have totally confused myself on material and size, the suppliers been using seem to have only limestone chippings and been reading on some posts that this is not suitable as pourous and can create deposits over time, another supplier has decorative gravel - on all the sites with limestone chippings they do say suitable for drainage but on sites on french drains say not to use limestone - would the second link be good- is that the right size - was going to line trench with geo textile fabric and also the pipe, only wanted to go for one type of aggregate if possible,

 

Any advice greatly appreciated,

 

Lawrence

Just realised the second gravel link isn't available locally - would need to go for gravel at 3 times the price of the limestone chippings - any advice greatly appreciated,

 

Lawrence

[Radian]

10mm Pea gravel is too fine and easily gets clogged with silt and mud.  20mm gravel is best for drainage. Limestone is going to end up like a subbase! Use a non-woven geotextile.

[jfb]

I wouldn’t use a membrane in clay. Can clog up the membrane. Could put membrane on top if soil on to of that.

[bob the builder 2]

was thinking of using this 

 

will be sitting on chalk around French drain with non woven between chalk and slate 

 

any views welcomed

 

Grey Slate Chippings 20mm - Slate Chippings | Gravel Master

[Miek]

40mm clean limestone is what is used around here (West Wales) for land drains, it depends on your local availability what is used, here pea shingle is twice the price of limestone. 

[PeterW]

2 hours ago, bob the builder 2 said:

was thinking of using this 

 

will be sitting on chalk around French drain with non woven between chalk and slate 

 

any views welcomed

 

Grey Slate Chippings 20mm - Slate Chippings | Gravel Master

Gravel or clean crushed concrete - should be £25/tonne loose or £40/tonne bagged - that’s decorative slate and I wouldn’t be burying it !

[Radian]

2 hours ago, jfb said:

I wouldn’t use a membrane in clay. Can clog up the membrane. Could put membrane on top if soil on to of that.

Yet Geocomposite drains are used for drainage in clay environments - sometimes in preference to gravel. I personally feel that the larger the surface area you can present to the silt as a barrier, the longer it will last as a drain. Without it, the silt will quickly find its way into the perforated pipe.

[Loz]

Thanks for all replies, I spoke to a couple of builders and does seem limestone chippings are what predominantly used for all sorts of drainage in west wales, they are washed and have gone for those, it is not a massive trench/drain doing so if needed to be sorted again further down the line then wouldn't be the end of the world, seems what everyone uses here - maybe being washed and where they come from locally the shedding of loads of sticky dust isn't so much of a problem, if there was 20mm gravel locally at a decent price would likely have gone for that.  Many thanks again, great forum,

 

Lawrence