Weekend Warrior FS2500 water tank repair

Depends on what the tank is made of. ABS can be fixed using an ABS type glue. However, most RV tanks are LDPE or HDPE (in either case Polyethylene) - those cannot be fixed with a chemical glue. Polyethylene tanks require plastic welding to permanently fix. I had a similar issue with a polyethylene water tank that sprung a leak where it rested on angle iron in my RV. I dropped the tank, pulled out a heat gun, cut up an empty plastic bleach bottle (poly), heated the surface of the tank (which was probably enough to repair the crack) and laid strips of the plastic bottle over the crack - melting it into the tank. I went a step further and used eternabond tape along the edge that rested on angle iron as a way to "pad" where the tank rested on the angle iron.