hootowl wrote:
...I noticed one line, however, that didn't fill with antifreeze. It comes up from the floor to under the bathroom sink, does a 180 and goes back down under the floor. Anyone have an idea how to get antifreeze into it or what the line is for?
That line is more than likely, your black tank flusher.
On the top of the 2 lines, there should be a black looking box where both lines flow into. This is your black tank anti-syphon valve.
I found it easiest to unscrew the lines from the anti-syphon valve and simply add some antifreeze with a funnel right there.
I also found that once I disconnect that valve, gravity will flow any water left in the line out both ends. A simply blow on the line and you can tell if all the water is out. Done.
Or, just use an air compressor and blow that line out through the outside hose attachment for the black tank flusher.
But, that's what it is.
Edit: Just saw Old Biscuit's post. You can still unscrew the anti-syphon and pour some antifreeze right there (or blow, as I see you've already done this).