soakaway details

A useful guide can be downloaded here

Or even from here:

Richard

You could try asking the local water company if they would allow you to feed rainwater into a foul sewer. I think the answer is normally No, but a friend recently asked and the answer was Yes in his case.

Fill it full of percolable (?) material and cover it with a waterproof membrane to stop soil getting into it.

In general a good mix of builders rubble and various shingle grades works well as a filler, and a sheet of plastic on top, and about a foot of topsoil on THAT is fine.

I believe you can now get precast concrete perforated pipe sections to line the walls but not sure. That is useful when you need to do it near other buildings - you can define the outflow better I THINK.

Trenching is easy - hire a mini digger.

You may need something bigger to dig a soakaway.

However, when designing drainage, you cannot get water to drain away below local water table: If this rises in rainy conditions, you need to work on a system to lower that, and that may nmean going a lot further downhill than you would like.

Have a look here