This has been a problem with many Jayco models for several years.
The FW tank (or tanks - our 22fb has 2 tanks connected by equalizing hoses) are very long and very shallow. They run the width of the trailer and are about 2.5 foot wide and only about 8-10 inches deep.
Take a look at this video at about the 50 second mark. You can see a couple views of the FW tanks during installation.