Never forget that in those 'extreme measures', there is always water in the tank of the toilet. It is the same water that comes in to your house. It may sound nasty but I live near the Gulf of Mexico coast. We learn where fresh water is when Hurricanes may break water mains, etc. Just a thought. If it creeps you out, but are still willing to try it, boil it for a few minutes, might do the trick. Of course if the water isnt clear, dont drink it