So, how does that make it a strong, durable solution for me?
Alternatively, when PVC is merely glued together, it creates a heavy and hard area in the material that is no longer flexible. So, if the PVC needs to flex at all, the glue prevents it from doing just that, and will most likely tear or create a hole in the liner, rendering it useless, creating a catastrophic leak in your shop.
When the liner has been welded (as opposed to glued), nothing is missed. And since the material has become one during the meld, the seal is just as strong as the material itself. See for yourself!