Here's a test for you. If you have any bottled water, see if it has an expiration date. We don't use it, so I'm not sure. Also remember, your fresh water tank is vented to the air, not sealed up. Do as you wish, but why do you want water in the tank? If you are at the storage lot and think you might need a a bathroom, do not use the camper, then you will have a mess in your holding tanks. And that mess will not be easy to get out next spring, after the liquid has evaporated. If you think you might get thirsty, pack a cooler when you go. Take some bottled water with you. I think you are asking for trouble, that is easily preventable.
One last test. Clean out an empty milk jug. Fill it with water and put it in the camper when you store the camper. Now when you go back in a few weeks, take a big long smell, then a big long drink. See if anything is growing in the bottom.
As a side note, people who sail the ocean in small crafts use canned water for storage and emergency. No air, no sunlight.Longer shelf life, but still has an expiration date.
Just trying to keep you healthy.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT