You don't say what year your Montana is. On new models the water is put in the fresh water tank by connecting to the city water connection and moving the valve to fill. In older model Montana's there is a small door in the rear that you can also fill with a hose. The fresh water drains on Montana's are usually in the back of the rig. A white hose comes out the bottom and either has a screw on cap or a valve.
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
2017 3500 Dodge Maxi DRW 4X4, Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, etc.