Rashid,
for ideas about living in your AS in winter, you can check our photos:
http://www.airstreamphotos.com/photo...r=1847&thumb=1
This winter it went down to -12c and we kept the water on. We have 2 light bulbs in the fridge, to keep the hydrant warm when the temperature outside falls around -2c. (2 bulbs, in case one bulb blows). In the back of the trailer, we have 3 bulbs on a thermostatic oulet that go on when it gets too cold (we have a thermometer we read in the trailer, check temp., reposition bulbs until we maintain safe temp.)
There is a "self regulating heat tape" that you can use on a hose. We have not tried it yet.
The place you want to protect the most is where the water gets in the trailer. This is the most vulnerable.
If it gets too cold some night and you do not want to disconnect (and drain the hoses,... a pain) , get an alarm clock. Get up once or twice to run the water a few minutes. Or else, you need to get out in a hurry with a heat gun to taw everything. (a hair dryer may work, a bit slow).
It is fairly possible that your weather get colder than ours. You may then have to turn off your water.
Chantal