I once had a grey water tank that was leaking out the bottom panel of my Bigfoot (the guy I bought the camper told me "it's supposed to do that when you over fill it"). I put up with it for about two trips before hauling it to the repair shop thinking the tank was cracked. Turns out, it was just the hose fitting that connected the tank to the camper. It didn't have enough flex to handle movement on the road and over time it broke a seal allowing it to leak. A new rubberized hose where the tank connected to the camper and problem solved.