Water from RV

We don't drink the onboard water. I'm afraid the little bit water that may have been in the tank will be funky after a few months of sitting. Plus I feel guilty for wasting the water... We buy a few gallon jugs of water at the beginning of our trips & refill those jugs as needed at the water kiosks that you can find in front of a lot of grocery stores (usually for about .35/gallon). We'll reuse them a few times, then buy new ones.
And now that we store our 5er in another town it would be difficult to sanitize the tank.