Regarding crushed rock beneath the ag pipe and above, do you recommend a smaller crushed rock such as 7 mm or larger such as 20 mm?
Also is this okay to lay in the trench?
https://www.bunnings.com.au/grunt-2m-x-10m-black-70um-multi-use-plastic-film-black_p0412365
Hello @DIYorPRO
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your surface drain.
I recommend using the larger 20mm rocks as they produce larger gaps which allows the water to flow faster going down. Whereas a 7mm rock will be more compact and slows the water down as it falls down because of the smaller gap. If you are building a French drain, I suggest using non-woven geotextile cloth for proper drainage. I don't recommend using builder's plastic as this impedes the flow of water.
Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.
If you need further assistance, please let us know.
Eric
Hi @DIYorPRO
Definitely don’t use a crushed rock as the powder will clog up and prevent drainage. I’ve always used 10-20mm bluestone or washed scoria, which are fairly common stone to use.
Nailbag
Evening @DIYorPRO
I have used 7mm gravel in my drain to rest and cover the stormwater pipe and also my ag pipe. It works extremely well to the point I wonder if I had just filled a trench with gravel would it do the same 🙂 Yeah, nah. but you get the drift 🙂 I agree with @Nailbag over no crushed dust as it will clag the drainage. I alos wouldnt use any plastic or even worry about geotex cloth as the trench will contain it and the socked pipe will stop the fines from entering the pipe.
Dave
