How Should the Flapper Be Installed in the Bathroom Fan?

Installing a Vent Flap on a Bathroom Fan

• 1

  Access the crawl space or attic above the bathroom.

• 2

  Follow the flex duct from where it connects from the outside vent to your bathroom fan. You may have to cut away the insulation around the flex duct to gain access near the bathroom fan box. Wear a dust mask if you must cut through insulation. Inhaling insulation fibers can be hazardous to your health.

• 3

  Measure approximately 6 inches above where the duct connects to the fan and cut the duct using a razor knife. You may need wire cutters for the coil inside the duct. Flex duct is springy, so measure the duct in a relaxed position. Do not compress or stretch the duct in order to measure it.

• 4

  Thread one of the O-rings over the duct connected to the outside and place the vent flap inside the duct. In the correct orientation, the vent should push open easily when facing you. Don't worry if your duct is larger than the vent flap. The O-ring will compress the duct to fit.

• 5

  Clamp the vent in place using an O-ring. O-rings slide through a buckle and clamp tight using a screw.

• 6

  Connect the other end of the vent flap to the duct connected to the bathroom fan using the other O-ring.

• 7

  Test the vent flap by turning on the bathroom fan. If the motor is running but there is no air circulation, the vent flap was installed backward. To fix it, just unscrew the O-rings and flip the vent flap.