Tanks sizes?

On our class c and on the tt before hand, we would fill the fresh water tank until it started coming out the spout we were putting it in. We knew it was full. That is if we were gonna fill it. Yes you can check the guage inside, but the guages are never 100% anyway, especially on the gray and water tanks. I would imagine with that small of a unit, that your tanks are not over 30 gallons each. Our Class C shown below has a 30 gallon fresh and 29 gray and 29 black. The number for the size of the tanks won;t really matter for you. It depends on how you use it and how thrifty you can be with the water. Trial and error will be your biggest benefit. Go camping in it over a weekend. Use it and see how fast things fill up. Figure out how to cut back to make it last longer. Things like an oxygenics shower spa do help. With the shower head and learning how to manage our water better, we've been able to go an entire weekend on our tanks (if using fresh water, then yes we had to replenish some) in the Class C. Where as in the TT we had, which had tanks twice as big, we couldn't go an entire weekend. Main reason was because we did not manage well. Go to a park with full hook ups, but act like you're without hook ups. And see how you do. Get full fast? Dump and try to do better.