My main drain stack that goes from the ceiling of the basement into the floor is rusting. In fact, there are certain weak spots where the rust is ‘bubbling’ up. It doesn’t leak per se, but the rust stains can be seen oozing down the stack. The stack itself is about 50 years old and made of metal, probably steel. The rust bubbles or oozing areas are about the size of a quarter or half dollar.
Can I patch these with that heavy duty plumber’s paste/spackle? What if I just put some tape over the problem areas? Would electrical or duct tape be best? I’m trying to avoid replacing the main stack.