Posted: 16/07/2012 at 09:30
Hi pash. I'm trying to do a similar thing but hole/trench just fill with water. Need a dry spell! We're not on mains for drainage so had a large soak away in the back garden for rainwater to channel into (also put rainwater tank in to harvest for watering) builder just lined the huge hole with what looked like that weed membrane and wrapped the gravel in a parcel. Thought I would do the same in a channel under my paths. Think that would also stop soil from washing in from sides too. These membranes are supposed to last over twenty five years? Buy on eBay at a reasonable price.
Think your crates would work fine as know some people who have just dug trenches, half filled them with a load of pea shingle leading to a deeper hole. Good luck