What exactly is so terrible as long as you're willing to take a small to moderate risk of getting a PVC pipe stuck in the ground and keep in mind the presented

What exactly is so terrible as long as you're willing to take a small to moderate risk of getting a PVC pipe stuck in the ground and keep in mind the presented cautions -- consider the water irrigation-only/non-potable until tested (possibly even if tested, although that's not what the site says)?