[Wiesehan]

Just a thought. A friend of mine developed a problem with one of the faucets in the bathroom (leaking) he purchased a new one and when we took the old one off, we found a dead bug wedged in the valve. After discussing and thinking about it, we concluded that at some time while filling the tank (or venting it) a bug got in the open fill hole and eventually found its way into the water line that supplied the bathroom. Leaving the fill cap off may not be the best idea, even if it is only for a few minutes.
Don