There are two ways that water can feed to the water tank. Either it comes from a gravity fed hole in the side of the unit to the tank, or it comes from a pressurized hose that has a valve to direct it.
I have had a unit with a valve, and I had to direct it either to the water tank, or shut off the water tank feed and it went directly to the taps.
In any case, when connected to city water, water did not backfeed through the water pump to the water tank.
The big however is this.. you want to live it in, and having a unit with it's own water tank onboard is always better than being connected to an outside tap when it's freezing outside unless you are really careful about protecting that line.
Do you need the space the water tank takes up? Why not just leave it there?
