Well, I looked under the bathroom sink where the city water inlet is located along with the water pump. There is a T connection between the outlet of the pump, the city water inlet and the in-line water filter. So if your plumbing is like mine it would appear the check valve in the water pump failed.
If you have a Shurflo pump like mine it has a 2 year warranty so you should be able to replace it no cost.
I think I am going to install a stop valve on the outlet of the pump so I don't have to rely on the internal check valve.
Dan (RVM67), Yvonne & 2 nutty mutts
2015 Flagstaff V-Lite 30WFKSS; 2012 Sierra 2500HD Crew
Home is behind, the world ahead, and there are many paths to tread...