We have a new tt and the underbelly is completely sealed and we were told that the heater pushes heat into the underbelly where the tank is. We will be camping in the next couple of weeks where it may get a little cold. If I keep some water in the fresh water tanks and with the heater running will it keep it from freezing. We will be connected to city water but at night I plan on disconnecting the city water and just use the water in the fresh tank as needed until the next day when we will reconnect to the city water.
I know of people that camp all winter in rv parks in Oregon and leave their trailers hooked up to the parks water and leave a faucet dripping and the grey open. Some use heated water hoses, but not all.
We've had the water in the hose for city water freeze up once when overnighting. No problem with the camper but it sure makes rolling up the hose in the morning a hoot! Since, I've disconnected and drained it before going to bed when expecting 20F at night.