I need to replace the vent pipes for my hot water heater and furnace- they're 3", 4" and 6"diameter and made of sheet metal. The duct assembly is held together with short sheet metal screws-- and I'm not sure how to start the screws in the new vent system.
I always thought sheet metal screws were self-tapping but doesn't seem like you could push very hard to self-tap without bending or crushing the pipe- especially the large diameter ones. Do I need to drill a pilot hole or what?
Joe