Pentair 261152 Replacement Pool Filter

Is this PVC or cardboard? Installed this valve on my Pentair DE filter September 2nd. Everything went together easily, all hand tight on the unions and sealed perfectly. First week of December went outside to water running down the patio. The nuts on both unions have developed multiple cracks and one separated and the fitting pushed out far enough to clear the seal. Amazon was no help it was just past 90 days. Contacted Pentair and their solution was to email me a list of places where I could purchase parts. This unit is molded and glued so the unions can not be changed it would require cutting the old ones off. This would not leave enough pipe on the upper on to glues a new piece on. For what? Another 3 months? Stay away from this thing. Nuts just fell apart.