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.
Best Answer
Be quite difficult to use a normal abs coupling here. The couplings have a stop built into them and you typically need flexibility in the two ends being joined. These look concreted in. If the connection is going to receive concrete on top of it I don't see any risk of this separating. Rubber does tend to age, get brittle and crack over time. I'd probably just embedded it in concrete on all sides, if the rubber does die overtime at least you still effectively have a concrete pipe directing the effluent into the other portion of pipe.
One thing I've done in the past is to take a hole saw and drill out the stop in a standard abs coupling, then slide the coupling onto one side of the pipe, abs glue the two sides and slide the coupling over top the two pieces. The sides need to be quite clean and I did this with 2" pvc last time. I am not sure how much force would be required on a 3 or 4" abs to pull the coupling over the glue. I don't think I'd do that in this case.