We have a 12" crack in the bottom of our RV black tank. The RV is a 2004, the dealer says they made this tank out of LLDPE. We are doing a temporary patch while we wait for a tank replacement. We have thought of Flexseal rubberized tape, and we have looked at Loctite Plastic Bonding. We were told by the dealer, do NOT use epoxy. However he was not able to make a recommendation. Apparently LLDPE is not simple to patch. (Also, definitely LLDPE, not LDPE.) Could you-all suggest what to use? Thanks for any advice!