Holing tanks size

My '03 Fleetwood TC has about a 33 gallon fresh water tank. The black and gray are about 22 gallons each I think. This works for our family for a 2 night stay just fine. The gray tank will hold about 4 showers plus other hand/dish washing. I think I could probably go 5 days or more on the black tank but I've never tried. Fresh would probably last us 5 days too.
By the way, I owned a Palomino truck camper once; I won't own another one. The construction and materials were very poor. Some people have said that a Fleetwood camper isn't that great but mine is miles ahead of the Palomino I owned.

Don't count on big gray water tank on any TC.
Some come with 20, some with 30 gallons, but even when you have the capacity, don't try to hit the freeway with it full, since the rear location does nice trick to COG.
Fresh water tanks usually are much bigger than grey tank, so I am taking advantage of outside shower.
Worse come to worse, get the dump tote.

Also if you are careful and at times reuse water you can make it go a lot further. I am by myself in a Bigfoot camper and can make the black tank (15 gal) last for 2 weeks. If you are in a place that it is alright to do it. Catch the sink water wash your dishes and then throw it out. Don't do this in Bear country! As to the shower it will last longer if you do every other one a bucket bath. The outside shower is a great idea if it is warm enough.

We find we can go longer boondocking by showering outside. You may also want to look into composting toilets. That would eliminate the need for a black tank which could be re-purposed for grey water.

We boondock almost exclusively and never really worry about the grey water as you can drain it into a hole in the ground or a container to get rid of it.We also have a black tote(for poop) we use for long stays if we have the ATV trailer with us which we carry more water in 25-50 gallon barrels and larger 25 gallon propane tanks.And also,a porta-potti is never a bad idea to have around out in the sticks.

Holding tanks just never seem to have enough capacity for longer stays in the hills in most RV's.Tenters and hikers just dig a hole and bury there stuff out here atleast.

You can buy bigger tanks, but you have to have somewhere to install them. Are you anticipating running out of grey or black? I don't know of any TCs that are in the 90s or early 2000s with very large holding tanks. You'll be no worse off with a TC than a tent, of course.

For us the black tank is the one that runs (so to speak) out of capacity first. This is compounded by the shower drain going into the black. I'm with Rutz on this one. With me doing my #1 business outside as much as possible, we can go at least 7 days, maybe 9 days, off grid and off road with these tanks:
fresh: 18 gallons
black: 14 gallons
grey: 12 gallons
We host 24 bottles of waters in the space in front of the wheel wells, and another 24 bottles on the floor behind the front seats.
We host 5 gallons of fresh water in sturdy gallon jugs (not milk jugs) in a cabinet on the floor near the door.
We wash the dishes in a plastic pan in the sink and dump the grey water outside away from camp.
We take military grade showers sitting on the pot with another plastic tub on the floor to catch most of the water that would go down the black drain, dumping it outside after use.
The upside is that you don't have to carry all that black and grey liquid/semi-liquid with you.
We have a pop up shower enclosure for using the outside shower. Works great.
We have learned to live with small tanks and that carries a certain satisfaction.
jefe

I have

33 fresh
33 waste
33 gray

I've had larger on an Arctic Fox, but the weight was redonkulous. :)