First, we have always traveled with about 5 - 6 gallons, enough to flush and wash your hands! Drinks, bottled water and beer. And we have never had a problem. Since we never dry camp why keep 40 gallons of water slosh ing around in the tank and growing algee! At 7.5 lbs per gallon, that is an extra 300 lbs I have to carry, I could think of many other things that I would want to haul around than 300 lbs of water! Next I am curious, the weight police on this site are quick to point out that on your 250/2500 rig you might add 10 lbs. Of fire wood, and put you over your RWVR ABC's soup rating, but an extra 300 lbs of water, "no big deal..."! Just saying?