[beeje]

There must be million threads/posts on winterizing campers on this site and many others. I have been using the KISS method for over 15 years. It does not get any simpler than this.

1- make sure ALL water /waste is drained from tanks/water heater etc.( as much as possible)
2-Bypass water heater
3-(May not be not necessary) but I do it. Tilt camper so freshwater drain is on the low side.
4-pour 3-4 gallons of antifreeze into the fresh water tank.
5-Turn on pump (with all fixtures closed)
6-Open one fixture at a time (hot and cold till you see pink
7-Let some antifreeze drain into the sink traps.
8-Done 15 min tops.

In the spring fill the fresh tank and drain a few times while running all fixtures flushing out the antifreeze.
After you deem it good enough, fill tank again adding a cup of blech (to sanitize). Run all fixtures till you smell bleach. Let sit 1 day. Drain tank and refill while running a few tanks of fresh water though all fixtures.

Note:IMHO The line that is between the fresh tank and the pump does NOT get winterized using the on board winterizing valve. This line is flexible and sags along the way and water will collect in the low spots and freeze.