Infill drain trench

[Ashworth1]

I have nearly finished installing new drainage pipes for my rain water prior to having a drive laid. I was going to use the soil that was removed and put it back over the drain pipes (mainly clay) Is this ok or is it better to use MOT type 1?

 

[Scarlet Pimpernel]

Pea shingle. 100mm depth. Although clay has different requirements to Plastic. It should have been bedded on similar.
Excellent guidance here
https://www.pavingexpert.com/drain02

Edit: the BCO may have some uncompromising comments to make.

 

[Hugh Jaleak]

As above. Bed, surround and cover with peagravel. Excavated material can be used for backfill, but initial layer needs to be free of any large lumps of stones that could damage the pipe. Once that's sorted, rest can go back in on top. Allow for settlement, especially if you are laying new drive on top!