Here's my 2 cents: 1. I have never used the tap water for drinking. I carry drinking water in plastic jugs of varying sizes. 2. I carry enough water in plastic containers (the 10 litre ones are easiest to handle) to pour in the water tank if need be. I just keep the jugs either in the truck box or in the bathtub. I never have to worry about whether I can get hooked up to city water. We always have enough for two of us to shower. 3. I have been known to plug the tub when I have a shower, then scoop the water into the toilet. The grey water tank will almost always get close to full before the black water tank.
It may seem like quite a performance, but there are only two of us, so we don't need to carry 1000 gallons of drinking water. We usually have a 4 litre jug on the counter. We use a pickup as a TV, so there is no big deal to carry some water in the box. A while ago, someone posted about a neat little water tank and 12v pump he kept in his pickup box. I am definitely going to look into that idea.
2012 Jay Feather 197 w/pull-out
1997 GMC Sub 1500 4x4;
or 2015 Ford F150 4x4 SuperCrew EB