Wow.. So glad my 2019 Rockwood has a regular fresh water hose fill up front where the tank is. My water flow at home is 5 gallons in 30 seconds (I timed it and that's how fast it fills a 5 gallon bucket from the hose?)
On an empty tank, with a 55 gallon cap, I just let it fill for about 4 minutes, and it's full enough for me and has not overflowed or not taken the flow at that rate?
All the other water hookups is at the rear of the rig, (city water, water pump, filter, etc.)
No issues with using the rigs fresh water storage and water pump.. Really have not even hooked up city water to it yet... Just like using the tank with water I carry.. ha, ha... Just a weekend camper so no big deal..
Good luck! Mitch