Here is a very good thread on PVC elbows (which I have):
http://www.ericsonyachts.org/infoexchange/showthread.php?7008-PVC-Elbow-Thru-hull-Replacement
http://www.ericsonyachts.org/infoexchange/showthread.php?7008-PVC-Elbow-Thru-hull-Replacement