PVC P-traps with threaded union bad idea?

Hi everyone!

First-time poster here, but I wanted to say that I greatly appreciate the community and all the knowledgeable folks on this site.

Anyways, so my buddy and I are in the process of gut-rehabbing a duplex into a tri-plex. Note that we are not tradesmen, so we are learning as we go!

We completed the DWV rough-in, and just water tested the system today. We found that a number of the 2" p-traps were leaking. I believe we have a total of 12 throughout the place (3 washer standpipes, 3 shower drains, and 3 floor drains).

We installed the traps in the link below, which have a threaded union. That joint is where all the leaks were found.
https://www.homedepot.com/p/NIBCO-2-in-PVC-DWV-Hub-x-Hub-P-Trap-Fitting-C4895HD2/100342771

It's important to note that we did not go around and ensure all the p-trap joints were tightened prior to testing. Maybe that's all we need to do? I believe that particular type of connection should not be taped/doped, correct? Do you think using the screw-type p-traps was a bad idea (vs. a fully glued p-trap) since all of them will ultimately be buried in walls or ceilings? Or should we be fine if we tighten everything up?

Looking forward to your feedback!

Thanks,
Michael

 

If the trap will remain accessible (not the ones you are talking about), I would opt for unglued traps. They are really nice when you need to make changes. If you put a trap adapter at the wall for the kitchens and lavatories you rehab in the future, you will make things better for the buyer, and maybe easier for you.

I don't know if the traps you installed are approved for inside of walls.

 

Do you know where I can find out more about this? Is there a proper term to use for these kinds of p-traps? All 12 will not be accessible once walls and ceilings are drywalled.