Banjar, you may do alot of dry camping at rallys for picking and can use a full tank of water. You have to consider the cost of hauling that full tank, gas mileage and wear on your coach chassis springs,tires drive train etc,etc.
Water weighs 8.33 per gal. if you have a 100 gal tank thats 833lbs added to your chassis. I have three holding tanks in my coach 2 black and gray if full would be another 1208 lbs than you add 10 gal WH, LP tank, and a 75gal gas tank. The weight of these items can really add up and most is just liquids. You have already added needs to carry your home goods,your body and food weights.
As you travel your weights will change and shift on your chassis changing the driving habits of your coach.
What everyone before me has said is true and you can add what I have said to it. Not trying to tell you what to do thats your choice but just consider what we have all said and use your best judgement.
Most RV'ers travel with enough water for use to next destination. When your parked in camp site fill to hearts content but DUMP before going back on road and save yourself some money for a new banjo. Good and safe travels.