We always travel with a full tank. I know the quality of the water at my house. We also drink only bottled water (we buy gallon jugs, usually enough for a gallon a day for the two of us). Since we mostly dry camp, we like the convenience of having a full tank. Some places we go have hand pumps in the national forests. That is fine but we try not to drink it and use our bottled water. Thirty years of rving and never had a stomach problem from water.
Our tank is 30 gallons. Sometimes, we also carry a couple of 6 gallon Jerry cans of additional water.