PEX A to 1 1/2" Sch 40 PVC outside home

[cnb8869]

DIY'r here. I have a 3 year old home, built in 2020. Heavy clay. Off the road about 240'. When initially constructed, plumber took 1" PEX A, from inside the house, through the foundation (basement wall), and transitioned to 1 1/2" sch 40 PVC about 15' from the house (now underground), and took that 1 1/2" sch 40 pvc all the way to the meter. Fast forward 3 years -- the transition sch 80 pvc fitting broke, at the threads. Did not freeze, we'er 42" below grade . PEX had brass male threads attached, into the sch 80 fitting, then glued to sch 40 1 1/2" PVC. The threads on the sch 80 fitting broke. I dug up and replaced. Was he wrong? Why did it fail? Did he just overtighten, or did settlement try to pull the pipes apart and failed the thread?
(ignore the larger 2" electrical conduit in picture..although it was in same trench).

I never bothered to track down the plumber. Maybe I should. I want to understand what went wrong before I talk to him.

TIA!

 

[Jeff H Young]

Get rid of the pvc female threads by watever means it might be easier to save the pex adapter and screw on 1 inch coupling brass and then a 1 1/4 x 1 inch male adapter or whatever but dont use female threads of plastic under pressure , including at the meter tailpiece never usew them again . live and learn

 

[Sponsor]

 

[Reach4]

It is best to avoid female plastic threads, although your PVC threads look like they would be contained by the pipe.
When working with longer PVC, there are some thermal considerations. https://www.charlottepipe.com/Documents/PL_Tech_Man/ExpansionandContraction.pdf