I am reviving this thread to report that on my last outing (1st time using the Airstream for this year), out of the blue, the water pump kept cycling on/off every few seconds when all taps were closed.
Oh No, thinks I. I have a leak somewhere! I searched all the plumbing that is visable from inside the coach and couldn't find a leak. So, after thinking about it awhile, I went outside and discovered the water exiting at the city water fill pipe (it really shot out when I removed the cap and turned on the trailer's water pump).
So, like some of you I decided it must be a failed check valve but when I started to look for the valve, like some of you, I couldn't locate it.
One of guys from my WBCCI unit noticed me looking around in the trunk area of my trailer (if you ask him he'd prob. say he noticed me looking bewildered). He agreed that it must be a bad check valve BUT he showed me what he had done to his trailer when he had this problem.
So, stealing his idea, last week I made the following repair:
'Forgot about locating and removing the check valve. Instead, I got a 1/2" lever valve (about $5.00), removed the short stub with the hose threads from the end of the pipe on the trailer. Using a bit of thread tape, I screwed the valve on in place of that stub.
Then, screwed the stub with the hose threads onto the outlet side of the new valve.
This modification adds about 1 1/2" to the length sticking out of the trailer. In my case, I do not think this will cause any clearance problems 'cause it is located between the rear bumper and the rear of the trailer, on the road side. So, I think if I were to snag it on anything I would have to, first, bash the coach body and/or tear up the bumper (either of which would have me overlooking the damabe to this water inlet.)
It works great. 1/4 turn and it's open for hook-up to city service or 1/4 turn and it's closed for using onboard water supply.
Now, here is what I think is an extra benefit to this setup (beside being a simple, quick, cheap solution to the check valve problem): when I am hooked-up to a water source and am going to be away from the site for the day and evening, I can walk to the rear of the trailer, turn the lever a 1/4 turn and not worry about what would happen if a pipe should develop a leak inside the trailer while I am gone.
A real neat feature, especially with the daisy-chain water systems used a some rallies.