How to Winterize Water Tanks
Disconnect the RV: Disconnect the RV from any external water sources.
Drain the tank: Drain the fresh water tank & any remaining water by opening all faucets, shower heads, & sprayers. You can also open the fresh water drain on the RV's undercarriage.
Drain the water heater: Remove the plug from the hot water heater & let it drain.
Bypass the water heater: Use a water heater bypass kit to prevent antifreeze from filling the heater before reaching the pipes. You should also remove or bypass any inline filters before adding antifreeze, as it can damage them.
Add antifreeze: Pour 2-3 gallons of non-toxic, pink RV antifreeze into the fresh water tank. Circulate the antifreeze by openings the hot & cold water faucets until the liquid runs pink.
Flush: Once the RV is winterized, you can still use the toilet & wastewater tank. Add a small amount of antifreeze to the toilet bowl each time you flush.
If you don’t want to disconnect from your water source in the winter then you will need to get a heated a hose, which requires 120V electricity. You will also want water tank heater pads to put on the bottoms of all your fresh & wastewater tanks & dump valves to prevent freezing.