Bedding pipework running a gradient help - Bedding gradient pipework

[TerryH]

It seems pretty straight forward for bedding pipework which is running horizontally in the ground, as described in the 'Bedding Types' and 'Pipe Laying Basics' sections but how would you go about bedding pipework running at a gradient?
I am wanting to replace my old cast iron soil pipe with a new plastic one.
The current pipe runs down the rear of the house into salt-glazed pipe sections.
The cast iron pipe enters a short 45 degree clay bend about 2 brick courses below dpc then runs away from the house at approximately 45 degrees (looking at it in plan view) and also at a gradient of approx 45 degrees meeting the main pipe with an oblique junction about 1.2m away from the foundations with 3 socketed clayware pipes preceeding this.
It is a 1930's semi and only the main pipe seems to be bedded anything near correctly. The pieces mentioned above (45 bend,3 socketed pipes and oblique were just on mud.
If I replace the soil pipe, 45 bend, 3 socketed pipes and oblique with their plastic counterparts, obviously using the correct coupling to connect the new oblique to the old main pipe.
How would the back filling be done for the plastic pipework that is running at a gradient from 2 brick courses below dpc down to about 110cm depth of the main pipe?
Would it be stepped down?
As I would imagine that throwing gravel/granular material into a trench that is running at a gradient will just fall to the bottom of the trench!
Hope I have explained this correctly?
Thanks in advance.

[seanandruby]

Hi Terry, you may have but if not.... read this Don't worry your pipe bedding will stay in place, as most pipework is laid to a gradient, some very steep. Last week i had to lay pipes at 141ml per meter, surrounded in pea shingle. Is there a reason why you are changing all the pipework and oblique junction?

[TerryH]

Hi Seanandruby, thanks for your reply!
Yes I had already read the link you provided but it only seems to show horizontal examples.
The gradient I am talking about is approx 45 degrees (see attached sketches) I apologise for the poor drawings but you should get the gist!
According to this site, plastic pipe should be covered fully in pea gravel so if I replaced the clayware shown on drawings with plastic and this is running at a steep angle surely the pea gravel would all run to the bottom. (see green dotted lines in drawing).
Obviousley I would fill the trench first over the main sewer pipe so the gravel did not run into this part but I was concerned about getting a level fill on the gradient from the main back to the house wall covering all the plastic section?
Maybe the trench would have to be filled a bit at a time starting at the bottom with gravel then a bit of soil then working up more gravel then soil and so on...
I'm sure I am worrying about nothing here but I like to get things right!

[lutonlagerlout]

normally you would mass fill this excavation with 10 mm gravel
it often takes a tonne or more to fill holes like this
LLL



Edited By lutonlagerlout on 1333471214