Gary,
The low point drains on my '06 are under the pan that covers the potable water, gray, and black water on the curb side. They are radiator style drain plugs with left hand threads.
As for the anti-freeze question...I don't believe Airstream puts them on from the factory. It is another "add-on" that you have to purchase and attach to the "in" side of the on-board water pump and use the pump to distribite the anti-freeze to the water system. Just remember to bypass the water heater or you're gonna' use a lot of anti-freeze
.
I also have a fitting I attach to the city water inlet so I can use my air compressor to purge the water before adding the anti-freeze. You can never be too careful with these Airstream investments.
