I found them! In a very strange place...in the bottom of the main power access cubby, under the 30ft power cord, in the outside wall. A very awkward spot, to say the least. Small space, so small that one of the chincey valve handles was busted off. Looks like I need to put better valves in, so they don't keep breaking. Anyway, I'm very happy to have found them! Thanks for everyone's help and suggestions.