Marc Ilgen
New Member
I know this question will show my nearly-complete ignorance regarding plumbing issues, but here goes anyway. In the back of my house there is some sort of black valve/cap that is now leaking and starting to look a little moldy. What exactly is this? I don't even know what it is called much less what it is supposed to do. In any case, it is starting to leak and look a little nasty, as you can see. What should I do about this?