Go to the Airstream Westfalia subforum here. There are several threads on how to replace and where to buy the submersible water pump.
Subforum:
sprinter-source.com
Where to buy replacement at GoWesty.com:
Dealer ordered water pump and attachment 6 months ago from Airstream for 2005 Sprinter Westfalia, whith nothing in sight. Does anyone know of better ways to find what I guess is a Westfalia part. Thanks, Peter Dudgeon...,
sprinter-source.com
How to replace water pump:
A poster on the yahoo forum asked for directions for replacing our freshwater pump. I am posting them here as well. I just replaced mine [for the second time] last month. Here is how I remember to do it. The big problem is working, one-handed, within the confines of the water tank. 1...
sprinter-source.com
The attach files document the Airstream Sprinter Westfalia Water System with a focus on how to remove / replace the water tank resident water pump. Of particular interest is the evidence of an inline water pressure regulator - one less thing to carry!
sprinter-source.com
Other:
There are other threads on different water pumps with higher pressure and output, loose connections inside freshwater tank, using an ax to open tank cover, always-running water pump, outside water input connection issues and switch needed, etc.
Also, there is an annual Westyfest on the east coast over Labor Day (don't know if will happen this year or not). And there is an Oregon Westivus later this summer (don't know if will happen or not). These are great places to share information about these Westies.
Please follow-up and post whatever you find and do. Thanks.