The Brew Cabin

Hi
I need advice concerning the laying of plastic field drain pipe, to remove water running downhill toward the house.
We have excavated for a garage etc and have created falls to take the water away from our cottage, but still need to redirect surface water off a bank before it gets to the "levelled site"
I'm planning on digging a trench along the base of the contour and putting in plastic drain coil, with a 800mm (approx) granite drystone dyke, outside the line of the trench.
the drain will have constant fall and I hope to be able to pipe it into a collecter or sump of some sort, from there pipe it in solid plastic to another sump, which will be taking another drain and then away across a road to a burn.

when i put the drain coil in, do you have to line the trench with anything or can you just put the pipe on granite chip and backfill with the same? I have heard that sometimes a plastic is used, is this correct?

the run of pipe is about 40m so is 100mm pipe ok?
i was hoping to link the two sumps with 100mm solid plastic pipe, and maybe 150mm for the road crossing?
does this make sense?

any advice would be appreciated

Have you read the pages dealing with Land Drain Construction? This shows standard construction cross-sections, including the use of a permeable geo-membrane which is now a recommended practice.

The diameter of pipework to use is determined by the size of teh area being drained. Generally speaking, 100mm diameter is adequate for most residential purposes. 150mm for the solid pipe should be more that adequate.