Probably plastic:
On October 6, 2017 at 18:01, Grasshopper said...
I also pointed out to my boss that the subs hadn't used a drop of pvc glue on any of their joints. Apparently my boss talked to them about that because they're now using pvc glue, as I ran into it today. But, even if they go back (they say they're going to) and glue their joints...that still leaves the ones that are under ground and I highly doubt they'll dig it all up again.
Grasshopper was bothered that no PVC glue had been used. That's not a reasonable thing to point out if the pipes are metal.