Do you have room to drill a hole in the tank that eliminates the pinhole or is too close to the crease ? If so put a bulkhead fitting in place and then use a pipe plug in the bulkhead fitting. The hole for the bulkhead fitting should remove the pinhole and solve that issue. I see this place also has a poly patch kit as well as a poly repair gun kit in you want to try this option. It's a PDF page that shows bulkhead fittings, the poly patch kit and the poly repair gun. http://www.sprayers.com/SprayerCat_2007/191-192.pdf | 
Poly water tank leaking, any fix?
