One of several reasons why we buy drinking water...Edgar.
Edgar climbs into our cistern at every opportunity. How do we know it's Edgar? Simple. He has the black mask. We should have named him Zorro, but he just looked like an Edgar. Not to be confused with Bob or Tim. They don't usually hang out in the cistern. They frequent our shower. (Although we did fish Bob out of the cistern yesterday. I guess Edgar was being a bad example!)
So, when they say, "Don't drink the water!" There's a reason!