I keep noticing the profile pic showing the tank with pipes below as being "wrong", and the one with the pipes above as being "right". I think I have the wrong one at my cabin. Thing is, I'm not sure what these tanks are, or what they are for. The one I have is about 20 gallon, by Sears, and I assumed it had some kind of rubber bladder inside. It has a standard needle air valve on top, like what you have on a tire. In my mind, I decided it was some kind of pressure "storage" cannister to limit the number of cycles the pump would have to turn on. But now I have the idea that what I have is wrong, and I'd like to know 1) if that's true, and 2) why it's true. What do these tank things do, anyways? Is bigger better? Should I have let the air out of mine? Before I did this, the system was pressurized and yet the tank was empty. I decided there should be some water in the tank so I let some air out. Now there's water in the tank, but I don't know how much. How do you "balance" these tanks between air & water? Or is it a "factory settings" situation that I've screwed up? This thing is obviously "floor mounted". Can I hang it upside-down and make it right? Do I have to replace it? The whole thing is bugging me now.