We camp in freezing weather and do not put antifreeze in the fresh water tank. We have 50-gallon black and grey tanks and dump a gallon to three in each depending on how long we will be camping. We carry drinking water. We put a 5-gallon Igloo water cooler in the shower and use it for the toilet. We switch to paper plate and bowls and pre-cook most of our food then just microwave it. Most of the time our water will still flow through the lines but does freeze below 20 every time and I have insulated every line. If you're going to do this for an extended time I would recommend tank heaters which I am going to add this year. Hope this helps.