Underground Drainage and Pea Gravel when and when not to use?

[BathDIY]

When I have replaced underground drainage previously have always added pea grave to the crown of the pipe.

Obviously, this is expensive, is it OK to backfill with soil as long as it's not full of sharp stones.

In other words, when do you use pea grave for underground drainage and when do you not?

 

[John D v2.0]

The purpose is to let the ground above take a bigger load, as the pea gravel will move around and settle with the ground and fill any voids under the pipe. If you use soil it would have to move with the ground.
If you are filling where settlement is unlikely and its in a flower bed you'll be OK. But if it's under a block paved path maybe less so.

 

[SpecialK]

https://www.marleyplumbinganddrainage.com/media/5423/pipe-laying.pdf

 

[noseall]

When I have replaced underground drainage previously have always added pea grave to the crown of the pipe.

Obviously, this is expensive, is it OK to backfill with soil as long as it's not full of sharp stones.

In other words, when do you use pea grave for underground drainage and when do you not?

Once it is surrounded.

 

[^woody^]

The gravel gives the pipe (and more so the joints) a firm base to avoid voids and stresses, and the surround is for a similar purposes and preventing punctures from objects. So despite an "expense" that's what is needed, unless you can find a similar performance from a different material.