alanz,also remove the line from water line to drain and let water drain from valve that its connected to. If you open all the lines the water will drain out of refer and you will not need RV-anti into ice maker. Use a sponge to remove water from container for making ice than use paper towels to dry completely. Don't forget all traps at sink locations and washer drier location, your shower inside and outside.
You can pump RV-anti thru all plumbing and leave some in toilet drains to protect seals.

Close your bypass valves for hot water heater.