[FlyingAroundRV]

Originally Posted by JRTJH

If you remove the roof vent fitting, the tank (with vent attached) should slide down. Once the tank is on the ground, you can cut the vent pipe at the tank. To install the new one, you can position the tank below the trailer, install a new vent stack (12' section) through the roof, glue it to the tank fitting, push the entire assembly up into position, The vent pipe will rise through the roof. Once the tank assembly is reinstalled, cut the vent stack to the proper height above the roof, reinstall a new vent cap and reseal. You may have to open a wall to access the vent stack if there is a strap securing it in place. I've only seen a couple of trailers with straps, most just use the wall and the roof cutout to hold the vent stack in position.

^^^This
Looks like the way to go IMO.