I have a 2019 Thor Gemini 23TR. I'm winterizing it. I drained the water tank by opening the 2 valves in the back of the coach. The holding tanks are empty. I put antifreeze in the water tank and then ran the faucets. They all ran until the pink showed up. This RV has a tankless water heater. Is there anything I need to do to drain its lines. I can't see any other valves but I'd like to make sure. I tried finding schematics showing the water lines but could find nothing. I sure would appreciate help on this.