I have a customer with a gunite spa that has a pvc fountain/pipe water feature that screws into a plastic/pvc flange at the bottom of the spa floor. The (underwater) flange the pvc fountain pipe screws into is stripped - completely smooth. Can this be re-threaded? Any know fix??? The flange does not look as though it can be removed and replaced with a new flange/plate with new threads. Any ideas?? Thx!