For those living far enough North to be concerned about freezing water lines.
This applies to all Airstream trailers and motorhomes with a demand water system. Demand systems typically have a plastic storage tank and a water pump that will activate shortly after a faucet is turned on. The procedure was used at an Airstream dealer for over 10 years with no returns.
Preparation: Have a source of clean compressed air, at least two gallons of non-toxic RV antifreeze, a male water hose/air chuck adapter, a 3' piece of 1/2" water hose and 1/2' to hose adapter, an adjustable wrench and clean rags.
Most, but not all years units have a side mounted fresh water tank drain. For those years that do not or for a more complete drain of the tank there is a drain plug in the bottom of the tank accessible through the tank enclosure access panel. Or it will be necessary to pump as much water as possible out using the units water pump.
DO NOT put RV antifreeze in the fresh water storage tank.
If you unit does not have a water heater bypass built in you can make one with two 1/2" pipe fittings and a short piece of tubing. If you do not bypass the water heater it will take an addition 6-10 gallons of antifreeze to winterize the unit.
To winterize: Remove the water heater drain plug. Apply compressed air to the city water connection using the adapter. Apply up to 60psi air pressure to the unit. When most of the water is blown out, remove the compressed air. Install or set the water heater bypass. Bypasses consist of 1-3 valves with the 3 valve being the most common. Set the valve(s) according to the manufacture's instructions. Replace the water heater drain plug.
Reapply the compressed air. Starting with the faucet furthest from the city water inlet open first the cold and then the hot side. Allow the air to blow out most of the water in the line. Cover the faucet with a clean rag to reduce splatter. Insure you drain all fresh water taps include the shower, toilet including the sprayer head and the outside service tap. With all lines blow out remove the compressed air.
At the units 12V water pump remove the line at the pump that comes from the fresh water tank. Using the 3' hose/adapter connect to the water pump and put the other end into a bottle of RV antifreeze. Turn on the water pump and open the faucet farthest from the pump. Allow it to run until antifreeze comes out. Monitor the antifreeze and replace the bottle before it empties. At each faucet/tap open both hot and cold until antifreeze flows. The excess flow will winterize the P traps. Should take about 1.8 gallons. Remove the water pump adapter and reattach the tank input line. Using a clean rag wipe down all surfaces exposed to antifreeze.
The science of RV Antifreeze is that it will shrink when it freezes. So minimum dilution and adequate flow through the system will insure no freeze damage.
Experience is that this method is the closest to foolproof there is. There are other options including just blowing it out.