I carry 2.5 gallon water jugs under my camper seats and lift them to the counter top when needed. Cheap to buy, always new, without that old water tank smell or taste, and I can get them at any large food store for right around $1 to $2 each. Recycle the empty plastic jugs when I get home. Simple.
Or,you can get slightly more complicated.
Air pressurize the water tank.
There are many ways to air pressurized the water tank. You can push the water anywhere with air pressure. Thus the ability to keep the water weight low in the camper.and avoids the negative weight aspect of permanently high mounted water tank for gravity feeding your needs.
I use a Zodi Extreme, outside the camper, on the ground, with camper through wall plumbing for my inside shower. With as little as 25-30 psi of air it pushes the water all the way to top of the inside of the camper where I have my shower head.
I've got a small air compressor (now using Ryobi cordless, instead of a Vair with 12VDC from the my larger camper or truck battery). That unit pressurizes my 1 gallon air tank to 100 psi with a regulator that outputs the air at 25-30 psi to the water tank. I can empty the entire Zodi Extreme 2.5 gallons of water on one tank of air. Nice when I travel alone, I don't have to keep pumping up the Zodi to get a good shower.
A smaller, simpler set up would be just the Zodi Extreme and use the included hand pump (like a bug sprayer) to pressurize the water tank, or any of the other makes of bug sprayer type shower water tanks. There could even be a way to hook up the hand air pump or even an air foot pump to your regular water tank.
Here's mine. Propane under the Zodi to heat my shower water.
And, my air compressor, air tank, plus hose can be used for other functions, filling tires, cleaning truck parts and camper door of dust, etc.
Additionally, the Zodi is also doing double duty as another water tank, beyond the 2.5 gallon plastic jugs that I carry.
