Whenever I am too far away from my settlement, in this case Sanctuary, which has a water production of 249, the water production drops to zero and the happiness starts declining. When I am in Sanctuary, all is fine, but as soon as I travel a certain distance, the water production drops back to 0. Can't the game handle a water production of 249?
Or could it be that the +200 purified water I have stored in a container (not the workshop) in Sanctuary is topping the water production?