I have the top of the line model of the top trailer made at the time? Wow. It doesn't feel like it at the moment!! 2 more weeks and it should be relatively stellar, I reckon!
So, I went out and bought a new thing so I could pull its valve/innards out and stick them in the old one. It turns out, when these things are new, the valve does not want to come out no matter what. They don't seem to come apart until they are ruined. Now I recall that's why I didn't take it out when sweating on the last new one a few days ago.
SO.. The new one I bought today is threaded female. I sweated a male threaded connector to the trailer plumbing and sweated on an elbow onto a threaded male adapter for the drain side (to which I attached the rubber hose). Perfect!
Threading it on there with all that pipe being against the floor was interesting, but I got it done without busting any previous sweat joints. Yay! That area is FINALLY watertight with or without the city hose, and with or without the drain valve open.
And yessir, the last new one I sweated on a few days ago was burnt to a crisp inside. Definitely buy these things threaded if you need one.
Oh, and I did it without burning my hands or igniting my socks. Finally I get the hang of plumbing just in time to be done. Ha!