When you look at the cap you will find there is an outside pipe that is from the roof, and the inside pipe that comes up from the tank. You need to make sure the sealant on the roof seals from the roof to the outside pipe all around the 14" edge, and up the pipe. The roof cap itself is about $4 for a new one, and it should take care of the difference between the two pipes.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel