I tapped into a 2" ABS pipe that runs underneath my concrete basement floor, and presently joined it using a Fernco coupling allegedly rated for underground use. (Unclear if this can be used indoors though? I was surprised the shielded ones I saw in stock at Home Depot didn't appear to be rated for underground use).
I had my rough-in inspected, though the inspector didn't say anything about it, and was mostly concerned that it wasn't leaking (it's not, and it's been there for about a year). But there's a bit of space between the pipes (perhaps 1/2") and I'm concerned they could come out of alignment (and I think you can see already the alignment is not quite perfect, though it was previously a continuous pipe; I could definitely force an alignment to make a rigid connection). The earthquake risk here is pretty minimal, climate zone 2, dirt is super rocky, some box elder trees in the yard not particularly close but with spreading root systems.
- Is this the main risk, that the pipes settle/shift sufficiently divergently to sever the connection? (And this risk is non-trivial?)
- Should I redo it so the pipes meet perfectly (no 1/2" gap)? (I would probably have to remove more of the concrete floor and replace that section of pipe to the right of the joint)
- More generally, what's the best thing I can do to improve and/or bomb-proof this junction (without tearing up the entire floor :)? Would a shielded coupler be a good upgrade?
Wye visible on the left to accommodate the drain I added; before I cut in, the ABS pipe was continuous. The entire length of pipe is underground below the concrete floor.