soakaway, membrane and running pipes to

Hi,

So far two soakaway pits have been dug 1m cubed. The building imspector is happy with the depth and isn't interested in seeing it again. I'd like to make a reasonable job though.
I've bought milk crates to fill one hole but would prefer to use rubble on the other.
1) What is the best type of rubble/shingle to use?
2) What parts of the hole do I need to line with membrane and what is the best membrane to use? I'm unclear if I need to line the bottom as well as the sides? I'm wondering if I can buy this membrane by the metre?
3) I have to run the pipes around something so I'm a bit worried about joining the pipe at the angles. Would I be okay to just go at right angles? The soakaway is just 5 mtrs from the building but the pipe will run for about 7 metres because of the detour. Will I get away with this if I go for a 1 in 20 slope?
4) Do I have to cover the top with concrete or can I get away with thick plastic membrane?

Many thanks

no membrane except on top of the rubble etc.then concrete on top 100mm wil do and then make sure you have enough topo soil on top if its in a garden area.you can use any bends you want ona rainwater pipe run.