Neat idea for your larger fresh water tank...
We too camp alot without hookups and usually spot the area that has a water spigot before arriving at the camp spot...
Sometimes of course this doesn't work out.
I carry four empty containers two 5-gal jeri-can types for fresh water and two 7.5-gal Aqua-tainer jugs for waste gray water.
I also have a two-wheeled folding hand truck.
Most places we camp at has a central located bath room and usually has an outside spigot so my daily game is take the jugs to the bath room area and dump down their toilet and bring back fresh water... I usually keep up with it pretty good...
We also have the cassette porta potty tank to roll up to the bath room as well and dump down their toilets... Sometimes the camp area allows you to pour out your gray water around the trees so I look for those signs too... Some places also has a designated marked area for your waste water as well mixed in with the camp sites..
This is one from Cloudland Canyo camp area...
This is my sink water capture setup using two aqua-tainers when one fills up then I move the hose to the second one...
I also carry a 120VAC water PUMP I pulled out of our washing machine before hauling off to the dump... It works great to fill things from a tank but of course being 120VAC I have to fire up my 2KW portable generator to run it.. The 12VDC model would suit me much better... My generator is always available sitting secured in the tailgate corner of my truck so no big deal...
I have seen one camper have one of those waste tanks up in his truck bed and used one of the mercerator pumps to pump his tanks out into the truck bed. Then he unhooked from the pump and kept the hose up high on the truck and took that to the dump area. Then he would gravity feed the waste into the area they wanted him to use for that...
Roy Ken