Can I run the bathroom fan vent into the already installed sewer vent? Previously it was just vented into the attic but is causing mold to grow up there because of the moisture.
A bathroom exhaust fan needs to be vented outside the home!. This sewer pipe is where the waste goes and will not provide a good or safe vent. Vents on the waste pipes prevent the water from being sucked out of the traps, or u bends, if the gasses can come back into the home there can be bad smells and at the worst methane explosions.