Water bladder

I stumbled on this style of water storage (bladder) while clicking around tonight.  Looks like some RVers stick these on the roof in-camp, probably filling up on the way in and then slowly driving to the campsite.  I see larger sizes, too.  Would save having to do some rounds with an Aquatainer for a long weekend.  As the sun warms it during the day you could even get an outside shower directly from it.  You'll still need to move waste water to the dump but at least you aren't bringing in fresh water, too.  Water is heavy though so I'd worry about putting too much on the roof...