I posted this to the list serve awhile ago. Thought I'd do it again just in case.

Hopefully this will serve as a guide for winterizing your Airstream. It reflects the way we have done it at our dealership. We guarantee no freeze up. Insure the holding tank(s) are empty and add the holding tank chemical of your choice. Drain the fresh water tank or pump out through the low point drains. Demand systems are more quickly pumped out. Pressure systems are more easily drained through their bottom drain. Most newer Airstreams (60's+) with a demand system will also have a drain plug in the fresh water tank. It will be above the belly service panel. Do not drain the water heater on a demand system at this time.

A pressure water system is one with a metal tank and an air pressure pump. It will typically have an air chuck in the tank cap. It uses air pressure to force water throughout the coach. A demand system has a pressure controlled water pump in the outlet line of the tank. The tank is plastic unless the system has been converted and the old metal tank left in service. A demand system uses a pressure switch on the output of the pump to sense the drop in pressure when you open a tap. It will then pump water until you close the tap and it gets up to about 45 lbs. Using clean compressed air and about 50 psi attach it to the city water fill. Open the drain (not the PTR) on the water heater and let the air pressure blow the water out. This scavenges the minerals out of the tank and extends the life of the tank. It is not a good idea to use air from an unknown source (gas stations etc.) as their air tanks quite often have oil etc. in them. Once the heater is empty close the drain. Inside with a rag or towel in hand open the furthest tap away from the city water inlet and let the water blow out. Do bath hot and cold side. Move back toward the water inlet being sure to do the shower/bath and toilet. Disconnect the compressed air.

If possible a water heater bypass will simplify the next step. Some coaches lend themselves to the installation of a bypass while others simply do not. A water heater bypass is a combination of 1-3 valves which will either block the water from going through the water heater and bypassing it or allow the water to flow through the heater for normal use. For pressure systems add enough RV style nontoxic antifreeze to the fresh water tank to fill the plumbing and p traps. 1-2 gallons plus the capacity of the water heater if it is not bypassed. Using the air pressure pump force the antifreeze out each of the taps running enough to displace the remaining water in the p trap ( a couple of ounces). Insure you open all taps cold and hot and the toilet. Drain any remaining anti-freeze from the tank.

For demand systems locate the water pump. Disconnect the low pressure or tank side fitting. Temporarily connect a fitting and line long enough to put the other end in a bottle of anti-freeze. Turn on the pump. Go to the furthest hot water tap and open it. Let the pump run until you start to see pink anti-freeze. For coaches over about 18-19 feet you will likely need to change the bottle about now. For units with no water heater bypass you will have to change the bottle several times. Once steady flow is established turn off the tap and open the cold side. Again, once flow is steady move to the next tap and the next including the toilet until you are done. Hope this helps. If I missed anything let the group know.

Because the water heater has nothing inside that can be damaged by the water left over from draining it, it is not normally recommended to put antifreeze in it. Next spring it will be more difficult to thoroughly rinse it otherwise.

Charlie