Grey valve open

I leave mine closed until it fills. then walk around and let it out. Takes about 3 min. Why? Having seen this happen even in stick homes. I have a irrational fear of something crawling up the hose into the tank, as well as a fear of insects building nests in the tank, and flying out into the TT. Foolish? Maybe, until it happens

But if you have never watched a person describe how they chased a snake across the bathroom floor after it came out of the sewer. You wouldn't understand.

So your thinking, What are the odds. Well, they are O / ZERO, if you keep the valve closed