That's true Lana, it is illegal in Utah and there are restrictions in Colorado, Washington and Arizona. However even in those states, it is incredibly difficult to identify and/or penalize houses that collect rainwater.
Love the show immensely. But the only person on the show that would even remotely qualify as a 'Survivalist" is maybe Daryl. But even then he was just more of an outdoors men who was thrust into a survival situation.