Water Tank Interim Repair

G'day all, On my last trip (Aust Day), as some are aware, my two front tanks started leaking. Being the front two it involved the potable and one of the non-potables. The leak occurred at the outlet barb, a blue tapered 3/8 thread barb with the 12mm pump suction line attached. I placed a bucket under the drip for one hour then measured the amount. I dont mind a drip or two but it was 600ml so I had to repair it somehow when back home. I tried thread tape at the camp ground but it made it drip faster as the eventual cause was a minute crack in the tank at the thread edge. The extra thread tape opened the crack further. After now having a good look with magnifying glass and light, I believe I found cause of the crack. Obviously because the barb has a tapered thread the more it screws in the more it stresses the female thread in the tank boss. As the tanks are blow moulded the plastic thickness around the thread in the tank varies. I just happen to have two tanks that are thin in this area and tightening the barb has cracked the thread boss edge. The two rear tanks are not leaking at all. I talked to several poly tank manufacturers looking for a product to seal this crack. They all said nothing will stick very well because poly is made from hydrocarbons (oil) and has a high wax content so nothing sticks. I tested several products from loctite plastic metal to sikaflex with the sikaflex being the best. It still peels off fairly easily but would be ok in an emergency. The tank surface was cleaned with acetone before testing to no avail. Eventually I went with welding the crack up. I did this with my adjustable soldering iron set at 260 degrees C and used a bit of scrap poly as a filler rod. This worked well on the non-potable ... I placed the barb in with thread tape ( gasfitters yellow not the white one) then heated the cracked area and filled it with a bit of filler rod. On the second tank I did (potable) I did the same but it leaked still so had to be done a second time. To make sure I placed a covering of sikaflex around barb and over cracked area and this has cured it .... for how long I dont know. Obviously I'm replacing the tanks with new ones but seeing as we are leaving Friday for a week in BT and doing the long weekends after Easter I didnt have the time to pull out two tanks and replace them. Its a good exercise to try a repair anyway ... hard to get a tank away from civilisation. Because there is not much head pressure against this area (tank is only 6" high) a good clean with soap and water around the barb and a plaster of sikaflex should seal this if it happens whilst travelling. I used Permatex Grey ( engine sumps) as it comes in a smaller resealable tube. A little tip when trying to apply sikaflex to things and shape it ...after squeezing it onto repair area, place gladwrap over it and mould it with fingers. Let it set well and just peel gladwrap off. The other way is to wet fingers with soapy water and mould it that way. Regards Anthony Explore this Great Land ...Do it Easy ...Tow a Bushtracker