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Old 06-09-2016, 05:47 AM   #1
3 Rivet Member
2014 Interstate Ext. Coach
fairfax station , va
Join Date: Jan 2015
Posts: 126
Lavatory Leak

Few will run into this problem, but this may help someone. 2014 Lounge EXT
The lavatory leaked; sometimes water would collect in a small puddle in the aisle. (not in the bathroom)

I then noticed wet spots under the van near the bathroom.

The lavatory uses a Hepvo trap, not a p-trap or s-trap.

Sorry, I didn't think to take pictures during the discovery phase.

The trap has a swivel nut on top and is meant to install directly to the sink drain body.

For some reason, Airstream added a bushing and swivel nut between the drain and trap.

Although hard to contemplate, the swivel nut had sheared in half and that's where the leak was.

The fracture wasn't readily visible.

Now this would seem to be an easy plumbing repair, but it's not.

There is a series of fittings in the cramped space and no slip joint or union. You would expect a slip joint in a waste assembly.

There is not enough room to insert the replacement screwed or glued connection parts. I tried a few things and contemplated many more.

In the end, after making me suffer, the gods smiled on me. The short remainder of the sheared swivel nut actually had enough thread left to connect with the drain body.

There doesn't seem to be any leak and the assembly seems stout enough to endure.

The leak was a result of both dubious design and QC by Airstream. The waste assembly design could be re-jiggered, but the space is so limited that install really needs to be done during initial manufacture..
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Old 06-09-2016, 06:25 AM   #2
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2006 22' Interstate
League City , Texas
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Originally Posted by VAtom View Post
Although hard to contemplate, the swivel nut had sheared in half and that's where the leak was.

The fracture wasn't readily visible.

Now this would seem to be an easy plumbing repair, but it's not.
I reviewed that manufacturer's web site so that I could comment semi-intelligently. They make mention of a "rubber seal" but your photograph appears to show a plastic part.

If it IS a plastic part, then your outcome is not necessarily "hard to contemplate" at all. Airstream built the plumbing systems in at least some Interstate models such that they do not accommodate the movement inflicted by road conditions (in fairness, other MH manufacturers may use similar methods - I don't know). Some of those plumbing components appear to be installed as if for stationary applications. My husband and I had to redesign our gray water system in its entirety after discovering that our gray tank had totally severed from all three of its lines (step-by-step repair descriptions here: Part 1, Part 2, and Part 3). We inserted rubber flanges and flex couplings into it so that it could bend when required rather than breaking (and it has worked perfectly ever since). The black water tank was also severed from its vent line, again, because there was no "give" in the system (that repair description here).

If there is no "give" in the system, something is going to break in response to applied stresses. It's basic physics. And materials science.

We have an older T1N Interstate (2007) and it's quite possible that some construction methods evolved since it rolled off Airstream's production line. However, another poster with a much younger NCV3 Interstate had a virtually identical issue with the vent line shearing off his black tank about a year ago. When my husband and I looked at his photograph, we could not detect any improvements in construction methodology. It appeared to be the same ABS pipe with comparable joinery to what ours had initially been built with.

So, the upshot of all this is that you may have discovered one more route by which plumbing failures can occur in systems that will break rather than bending in response to real-world conditions.

And no, these plumbing repairs are not easy!! Any time one is working in such a restricted space, there will be hell to pay in terms of effort. My husband and I tested our marriage struggling with ours. We later learned from another Interstate owner that if we had opted to contract out for the work that we needed, it would have probably been between two and three thousand dollars and would have required an extended stay in the repair shop (that owner stated that his had been in the shop for "months").

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Old 06-09-2016, 07:17 AM   #3
3 Rivet Member
2014 Interstate Ext. Coach
fairfax station , va
Join Date: Jan 2015
Posts: 126

Thanks for sharing your experiences. I reviewed your grey water rehab posts.
I had discovered your helpful and entertaining blog after seeing your Yeti post.

What I found hard to contemplate was not that a pipe to sheared off at a connection but that the nut actually sheared horizontally.

I would like to have put in a flex connection, but alas, no room. I would have to drop the tank like you did and re-engineer the whole drain/vent system.
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