Anti freeze into fresh water tank

Putting antifreeze into the fresh water tank and pumping it from there is a valid method of winterizing, but generally not the best method unless it's the only one available. It requires a good bit more antifreeze than pumping it from the bottles (you need enough to cover the pickup for the pump), it often results in more or less diluted antifreeze since frequently the tank drains do not drain quite all the water out, and it is a lot harder and more time-consuming to rinse clear afterwards. Still, it's a method that does work and a few RVs make it impossible, or nearly so, to do anything else.

I'd put it in the same category as winterizing without bypassing the water heater...both work, but there are better ways.