Advice wanted on buried pipes in kitchen

[jc2001]

I want to run a 40mm waste and 3 15mm water pipes (hot, softened + drinking) about 2m across a kitchen to an island unit. I am OK with digging the channel and adding DPM etc. but I want to know whether it is OK to bury the pipes directly in the screed or should I run them in a conduit. If so what should I use? I asume it is best to avoid any joints but I may need a 135 in the waste at the isalnd end which I would use a solvent fitting for.
Is plastic or copper better for the 15mm? I would prefer copper as I am used to it and have bending springs etc.

Thanks in advance.
Stig

 

[kevplumb]

try a search it was well covered a while back under buried pipes i think

here

 

[PEDANTICVINDICTIVEMAN]

I would put in a channnel using plastic in one continuous lenght, no joints no potetional leaks and no corrosion, I like Hep20 as I think it is more robust than other brands.