Holding tank valve how-to

[Carl L]

Carl Oh.? I got it.? For some reason I thought it had to do with hooking a hose up and running water into the tanks, which just didn't make sense, since it would run right back to the hose.? OK.? So I can just ignore the little cap for the most part.?

There is a fitting that will allow you to back flush a tank with a stream of water from a hose, but as you say, that ain't it.