Winter water protection

In winter I've kept the water tank full and had the trailer connected to city water with a hose. If the temps were going to dip below freezing I'd disconnect the hose and lay it on the ground so it will drain and not freeze up. The water tank would last me about 8 days flushing the toilet taking a navy shower every other day. I'd keep an eye on the temps reconnecting the hose when it wasn't going to freeze and refill the tank during when the hose wouldn't ice up while filling.

Only my fw tank is inside the trailer frame and insulated. The bottom is sealed with coroplast on the bottom to keep it dry. The heating duct running under the floor has about a 3 inch hole in it where it passes over the tank to blow heated air on top of the tank when the furnace runs. This has worked pretty well except when the temps were in the teens and twenties for a few days with single digits at night for 2 or 3 days. The tank didn't completely freeze but I think the pick up tube and water in the bottom of the tank had iced up and the pump couldn't pull any water from the tank. That was for about 24 hrs. The next day it warmed back into the upper thirties. We had aslo had about 10 inches of snow on the ground and the hose was burried under the snow. I had a 7 gallon water jug i had filled before the temps dropped and had sat it next to the kitchen counter just in case I ran out or water before I could refill the tank and or hook up again. The winterizing connection and tank connections are located there inside the corner of the cabinet. I was going to use the winterizing hose to draw off the water jug but it warmed back up enough and I was able to draw off of the tank again

Use a water circulating system. Enclose the bottom of the RV and have heat tape on the pipes.

I added an outlet and use a 600 watt heater on a mechanical thermostat for my waste tanks and valves.

Elaborate on "heated pipe"?

Best bet is to use your on board tank, refill as needed, and disconnect the city water when not filling the tank. If your fresh water tank is outside the RV, it will need heat, from the furnace, or a heating pad, and some insulation.

Fill your onboard tank and use it for fresh water.