What type of RV do you have?
My experience is with Truck Campers (Lance and Outfitter), fairly cold winters down to the singe (Fahrenheit) digits.
The fresh water tank has a low point drain valve. Turn off water pump, open all faucets, open low point drain(s) and let out all the fresh water.
Empty the water heater (remove drain screw).
Empty the gray and black water tanks. Might be a good idea to flush them while you are at it.
No antifreeze here. Basically unheard of for winterizing RVs over here in Germany.
Worked for me without any problems through near 0F winters.
