We used it once in the fall and never even turned on the hot water heater. My husband was going to take it in to get winterized and was told to do it himself. We followed the directions to the tee.
There are several ways to winterize a TT and often the directions for the trailer are sometimes vague. IIRC below are the three from the worst to the best ways to winterize. They all involve bypassing, draining the Water Heater and opening the low point drains along with opening all faucets, including the toilet and outside shower if you have one, etc. You also have to drain the water tank. After that you close the low point drains and all faucets. I didn't include all the steps so don't take this information or the below as being complete.
1. Simply blow out the lines using low pressure air like 15 to 20psi including the toilet and low point drains. You also pour like a cup of water in each sink and tub plus toilet. This can leave enough water that it can collect at some point in the plumbing and freeze and burst the line.
2. Simply pump RV antifreeze thru all the lines letting at least a cup going into each sink and tub plus toilet and low point drains. This is fairly good, but you might still have a little water mixed with the antifreeze, but unless your really expect cold temps like -20 should work fine.
3. Do #1 followed by #2.
Larry