I'm using a PVC glue, except it never occurred to me that it might to adhere to plastic (or whatever tupperware is made out of). I bought some tupperware-like containers (big plastic things) at Kmart for my DIY sump, but the PVC's I want to glue to it won't glue the PVC to the plastic. Do I just have to hold it together longer or do I need a different kind of glue?