I recently found the leak in one of the freshwater tanks in my 1984 Catalina 30. I also put some dye in the tank to verify the leak was coming from the tank.
I could not find the leak with the tank in the boat. Even after pulling it I could not find the leak until I finally pressurized the tank and found a crack about 3" from the bottom on the side. I was surprised it wasn't at a connection. When under pressure, water would just weep through the crack. It seemed to leak faster in the boat. It must have been a combination of the weight of the water in the tank and a pressure point near the crack.
I've done a fair amount of research of how to fix it but have not found anything that I am ready to try yet. Seems like welding it, with or without some more of the same type of plastic, is the way to go. A skilled hand may be able to do it with a hot knife or iron. There are also fairly expensive tools for this. To much heat and you have a bigger hole. Right now I am just using the extra space for other stuff. Anyone have any experience fixing a leak in a tank like this?
-buddy