many campsites will have water/electric and no sewer.
many campsites have no hookups at all.
we dry camp almost exclusively(no hookups) so we take a 6 gallon water jug and a 15 gallon blue tote tank, which we only use for the gray tank, since it will fill up 10x faster than the black tank.
usually adding the capacities of the black and gray tanks together will be way more than the capacity of the FW tank, in most TT's. rarely would the FW tank be equal to the added capacities of the B/G tanks.
so, if dry camping, you'll never exceed your holding tanks with a full FW tank.
your trailer has a 36g. FW tank, which includes the 6g. in the WH. your B/G tanks are 30g. each. this are pretty standard numbers for smaller TTs/HTTs.
you can go a long time without filling a 30g. black tank but not so with the gray tank. we can go weeks without dumping the black tank but the gray will have to be dumped every 3-4 days, therefore requiring the tote tank if you don't want to have to move the trailer.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC