We returned from our last trip of the season Saturday and winterized our camper on Sunday. We did the following items:

- Opened all faucets (kitchen, bathroom, shower, outdoor kitchen, outdoor shower, toilet) and let water drain from low point drain hoses
- Drained hot-water heater and left plug out
- Drained fresh water tank via gate valve underneath camper
- Hooked compressed air to the fresh water fill and blew out all lines
- Siphoned anti-freeze into black tank back-flush line
- Poured anti-freeze into trap of each sink, into shower drain and poured some into toilet

Given this...is it really necessary to siphon anti-freeze into fresh water lines?