Encasement arround the undergroung upvc pipe

Concrete pour...okay over pvc.

it is acceptable as long as it has 100mm min thk encasement all round the pipe.

If the encasing concrete cracks due to ground shift, it will possibly break the pipe. I have seen pipe put in a trench filled with sand to decrease the possibility of sheared pipes.

I am sure the material in the pipe (what is the impact of a spill) has a major influence as to how the pipe needs protected.

It not a case of chemical reaction but mechanical movement which could split pipes in intimate contact.

Lag the pipes with approved lagging to give air space this also allows pipe to expand and contract due to heating and cooling which if contained could stress the pipe and cause fractures.

Seems more appropriate to the embedding of metallic piping. Close (near structural) concrete contact with PVC pipe (with its very low expansion coefficient) will do more than free space (air gap) to prevent pipe splitting...wouldn't you agree?

At lease this has been the case for me where, on our property, soil imbedded PVC as ruptured on more than one occasion; but never the concrete imbedded PVC.

As to soil movements that could damage concrete, that of course is a possibility which would have to be taken into account...as to whether or not it's a likely possibility; or as to whether or not the potential risk caused by imbedded pipe rupture is worth protecting against.

Seems more appropriate to the embedding of metallic piping. Close (near structural) concrete contact with PVC pipe (with its very low expansion coefficient) will do more than free space (air gap) to prevent pipe splitting...wouldn't you agree?

Not necessarily PVC has a higher coefficient of expansion than steel, also exits through the slab should have some sort of separation to avoid stressing due to expansion and contraction. PVC can take a lot of flexing due to its elasticity but it is wise to take precautions.

Excellent......

Thanks,