Winterizing City Water System

[montanacamper-FUN]

I just finished winterizing my 2008 FF189 FBS. Piece of cake with the HW tank bipass and the extra tubing to suck antifreeze straight out of the jugs.
Took less then a gallon do all the fixtures. Then added some to the FW and BW tanks traps etc.
However I am unsure about the City water connection and plumbing. I was unable to get antifreeze to appear at the inlet by pushing on the backflow valve inside the screen on the inlet. Any suggestions?

 

[montanacamper-FUN]

Got it figured out by reading other posts.
I did not have a water filter but found the location where the filter would go under the bathroom sink and after disconnecting the joints all the water drained and I'm good now.