While, in theory, there is no reason that a material might be capable of making a product that meets both plumbing and electrical criteria, the only way of telling is the 'look for the label.'

Head of quality control, and they're the same? Now you're scaring me. I am sure that, as head of quality control, you had regular contact with the local UL rep, and had visits where samples of both material and product were removed by the UL rep for follow-up testing. Testing that included tests for aging, sunlight resistance, flame test, and a crush test, but did not include any pressure burst test. I am also sure that you are also aware of the control, and expense, associated with the UL label / marking itself.

More to the point, I've seen the myriad preparations PVC raw material comes in, and I simply cannot accept that the same material was used all the time, for all the product. Even within the same product, plant managers are constantly using different preparations. Heck, a short chat with the guy who feeds the stuff into the line will produce stories of 'the time we ran that awful stuff.'

I'm simply not buying that 'it's the same stuff.'