This has always been a decision based on your unique circumstances. Would you winterize your trailer if you lived in Los Angeles? probably not. The only "winter" in LA is rain and it rarely freezes. If you live in Minnesota you may have a different view about winterizing.

Here is my experience: In Southern Utah at 5000 ft elevation we get temps that go down into the 20s in the winter. That may be reason enough to winterize but since I do so much traveling in the winter down to the warmer deserts around Tucson, Organ Pipe NM, Death Valley, etc, I choose to keep my pipes from freezing a different way... I keep a little electric heater going at all times. the thermostat is at the power supply, not on the heater so I can set it at 40 degrees and forget it (the built in heater thermostat wont set that low).

This is what I did with my A-liner and it worked well so I figured it would work well with the Casita too. But two problems occurred. First the temperature fell to an unusually cold 8 degrees. Second the Casita is built different and the water lines are close to the outside wall and hidden behind cabinets. So they froze! Even with the heater on.

Luckily the pipe freezing wasn't real hard and no damage was done and a very nice lady on http://casitaclub.com set me straight on heating those pipes. Just keep all the floor cabinet doors open so the heat can get in. It works fine and I still don't winterize :)

So? Freezing. Let's see if we can get some facts straigh first..

1. Water freezes at 32°
2. Water in a vessel freezes from the outside in.
3. Water expands about 10% when it freezes
4. Water expansion will alwyas be int he direction of least reistance.