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Old 12-22-2019, 07:57 AM   #1
Rivet Master
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2007 Interstate
League City , Texas
Join Date: Oct 2014
Posts: 5,607
Atwood water heater - P&T valve plus additional leak

I've got a combination issue here that could represent something semi-specific to T1N Interstates, or it could be one of those situations where the two issues that are manifesting are unrelated. There is SO MUCH that goes wrong with Airstream Interstates that I've learned the hard way not to assume that two problems occurring simultaneously are connected.

The P&T valve on our Atwood water heater seems to be leaking more than it should. This is a new development. Various internet resources note that occasional drips from that valve are not a cause for concern, but whatever is happening now is different from what happened over the past 5 years, not that we've used that heater very much.

The water heater seems to be working correctly. It shuts off when it reaches temperature. It seems to build up no excess pressure. The P&T valve is not stuck in place, which can occur with older valves - I can open it manually and it lets off just a little pressure, as one would expect from normal operation.

This inquiry didn't actually start with the Atwood, however. What I noticed was fresh water dripping to the ground about 7 feet away from the hot water heater and on the opposite side of the van, every time I turned the hot water heater on, but at no other times. Weird as heck, eh?

We spent over an hour trying to source that second leak yesterday. We don't know exactly where it is yet, but we were able to constrain where it is not. It might be caused by a leaking backflow preventer on the city water inlet.

What we observed to start with was water dripping off the old propane line for the refrigerator that we removed 2 years ago. When we switched to an all-electric fridge, we capped off the distribution segment to the old fridge compartment, but we never stripped out the original copper line segment - it wasn't necessary, so why spend the time?

We de-installed that line segment yesterday during the leak chase, given that it was serving as a conduit for wherever the leak was originating. Clearing the old copper line penetrations top and bottom of the fridge cabinet allowed us to get an endoscope in there much more easily. That area is like the hinterland of the T1N Interstate - it's the most inaccessible area of the entire van.

On the surface, the logical explanation for the combination of the two water leaks is that (a) the Atwood is overpressuring and (b) forcing water out of the system's weakest link, which happens to be in the vicinity of the city water fill.

Of course none of this is happening while we are connected to city water. I almost never connect at all. And at this point, I don't get the feel that the Atwood is malfunctioning and overpressuring.

Anyway, my husband had to get up at 3 a.m. this morning to help land the Boeing Starliner which malfunctioned upon launch two days ago, and threw off the work schedules of several thousand people. We will continue to pursue this today after he gets some rest.

Meanwhile, has anybody else experienced anything resembling this?
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Old 12-23-2019, 05:11 AM   #2
Rivet Master
2013 Interstate Coach
Raymond , Iowa
Join Date: Jun 2014
Posts: 1,288
Early this year I had a leak where the fitting was connected to the back of the city water fill. It had nothing to do with the city water check valve per se, just the screw fitting connected to it. Then later this year I had a leak where the line connects to the outside shower valves. My leak occurred due to pump pressure alone. Not sure how much the line pressure would increase due to hot water, but doubt that pump pressure + hot water would be higher than city water pressure.
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Old 12-24-2019, 05:16 AM   #3
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2007 Interstate
League City , Texas
Join Date: Oct 2014
Posts: 5,607
What did you do in the way of fixes?

Any specific fittings that you would recommend as replacements / upgrades?
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