Tent Camped in Our Airstream!

[Itsatruly]

We just returned from a two week road trip to Black Hills, Yellowstone, and CO. Day one, the pump would run but no water. We finally stopped at an RV place and thanks to a very kind parts manager, he put in a new valve and pump worked great. But...down the road, every time we turned on the water, we realized it was coming out of the shower! My husband could not figure out how to get the shower to shut off! Consequently, we couldn’t turn on the water. So, you might think...Aha! At least they could take a shower. Nope. The hot water heater failed to light, so we had no hot water! Sigh. Despite these issues, we still had a great time but would appreciate any suggestions on how we might fix our problems! Thanks!

[AirstreamCSH]

Your Airstream is 15 years old at this point. I’d simply replace the shower body. In my 25’, for example, you access the shower body from a panel in the closet next to it.
Look for something similar in yours.