How to connect trenched 3" ABS to inside of house? Pics within

[OnlyinCali]

Long story short, I need to connect a 3" abs sewer line (freshly trenched) to the 2" ABS drain coming from inside the house. I am worried that something will break if the freshly trenched 3" sewer line settles at all. I did 5" of pea gravel below and 6" above the sewer line(all manually compacted every 2").

The problem is, the 2" ABS drain that is inside the house is already complete and cannot be pushed down onto the new 3". It looks like I'm stuck working backwards, from the sewer line, back up to the house drain. This would mean I would have to cram gravel UNDER the pipe AFTER it is glued up. This sounds like a break waiting to happen.... Do you guys have any better methods? Gravel then expanding foam under the pipe? I also thought of just using a 2" fernco but that would have to be buried in the concrete repair work that will be done to the side of the foundation(picture below). Or am I just being paranoid?

 

[OnlyinCali]

Any ideas at all? Sorry to bug, hoping to finish this up tomorrow.

 

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[Reach4]

I think your major question is whether you can connect the pipes and then fill in to support the pipes. I think the fill that is up against the pipe would be better to be sand rather than gravel. But yes, it OK to have the pipes in air, and then add the proper fill under and around.

A toilet should have a 3 inch drain. How do you only have a 2 inch drain coming from the house?

Anyway, when you transition from vertical down to horizontal, you need a long sweep. You can use shielded/banded couplings to connect if that makes it easier than gluing. https://www.fernco.com/plumbing/shielded-couplings/proflex-couplings I am not a plumber.

 

[OnlyinCali]

Thank you for the reply! You are correct, the major question is if its ok to backfill a "suspended" pipe for that 1 foot long section.

No toilet will be going through this, this is an addition to a few couple 4" main lines coming from the house. This is only for a kitchen sink/washing machine that is being tied into the main lines.