Just looked in my truck, and the clear stuff I got from the supply house was made by Cantex. I've never seen the gray offered.
That said ... while I can be quite insistent upon UL listing in many cases, PVC glue isn't one of them. As electure suggests, the folks at Oatey probably know how to glue PVC together.
I've never understood why we weren't held to the same standards with PVC as plumbers where primer is required. The only difference we have is that we are trying to keep water from getting INTO the pipe.
I've always used primer, and yes it has been the purple stuff but I'm careful with it where it is exposed so that it looks OK. On underground couplings, I really don't care about being neat with it. Still, it makes sense that the joint should be cleaned prior to gluing.
My experience has been that many joints that pull apart are due to too much glue. It tends to "over-melt" the surfaces and the hardened glue ends up being the only thing holding it together.
It also depends on the manufactuer of the pvc. sometimes the fitting and conduit are loose and other times they are tight. It also depends on the installer. I have seen guys dab a little glue on the and push it together no twist and not enough glue for the weld to occur. You can tell if you look at the break just where the glue was. Ob
This installation will always be a problem. Beyond glue problems, the flex conduit will get stiff with age and nothing will hold it together. The very best legal installation I have seen for this type of application has been hard useabe SOW type rubber cable. Not too useful for multiple circuits though and requires connections and JBs if there is room, and its ugly.
The very best not so legal method I have seen is a tough rubber hose like fuel service hose and hose barbs with clamps at each end. This is the best flex conduit on the planet. Too bad its against the codes. I wish they would make an approved rubber conduit because it takes abuse like nothing else.
