Just an opinion from an old veteran FGRV trailer camper.
With the limited amount of space in my Scamp
I am not interested in providing space for a large container filled with air that is used occasionally for transferring water.
When the kids travelled with us we did like, I believe it was Gina, and carried a couple of gallon milk jugs. The kids ran back and forth getting water. That worked unless it was too cold, too hot, too wet, or whatever, and then I did it.
Now that the kids are grown up, we decided that the tank we carry water in should be the tank we use water from.
Until last fall
we just carried nine milk bottles, eight in two of those plastic crates that hold four gallon jugs each and the ninth one at the sink. That works great, except the bottles are a little light
duty and we've had a couple of leaks
over about ten years.
Now, I'm not exactly sure why, but I decided to go up-scale. I added a nice expensive marine hand pump and made a shelf under the counter on the wheel well hat holds three of those blue bottles mentioned earlier. Two are for clean water, and one is the grey tank. I have a foldable hand truck set up for trucking them.
We haven't tried this out yet on a "real trip" but it works great in the driveway. Whether or not we will like this better is not known yet. If the six gallon bottles are a bit much, I think dropping back to about 2 1/2 gallon jugs might be just right.