WX says a big cold wave is dropping down out of Canada this coming next few days... I would judge accordingly...
I havent looked on the map but I think Round Rock is in the Austin area...
Our POPUP trailer is much smaller and a very small water system compared to what you most likely have. We too like to keep on camping in the winter months so the blow out method is our best course for winterizing. Here in Northern Va just gets cold over night sometimes and warms up the next day...
I cam drain my fresh water tank at the low water point with the sink spigots open and blow out the water lines using my 12VDC tankless air compressor. Then just add some pink stuff to the two p-traps I have on my trailer... The hot water heater will have drained down using the low water point but there is still some water in the bottom of it. It has plenty of room to expand if it freezes... Like at the house we always unhook any water lines connected to the trailer city water port...
Used to live in the Wichita Falls areas for a few years back in the 60s... Some of the coldest WX I have ever lived through haha... Learned what a blue northern was when we lived there...
Water lines will bust for sure if they have water in them and freezes up...
Roy Ken