INTERSTATE LEAKING GRAY WATER, PART 1: THE PROBLEM

We were in the process of replacing our electrical converter when we noticed something strange on the underside of our recently-purchased 2007 Airstream Interstate.

Water began coming out from where it should not have been.  We were draining stale water from the fresh water tank and had just barely run a bit of water through the wet bath shower drain when we noticed that it started dripping immediately.  

Furthermore, the discoloration and corrosion visible around this bracket opening suggested that leaking had been occurring for some time.  Mind you, this was a vehicle with just 26,000 miles on it, very lightly used (the previous owners reported little use of the water system).

Here is a wider view of the same structure (pic taken before the leak began), just so that you can get oriented.  Remember, this is a 2007 mid-bath - the grey water tank might be in a different location on other models and other model years.  That's the right rear tire in the background.  The "heat shield" is actually more like a cold shield because it was intended to protect the tank and provide some insulation, assisting an integrated heating element to prevent the gray water tank from freezing in cold weather.   

The situation demanded investigation and, boy, did we get a surprise when we took a closer look.

My husband removed the "heat shield" and crammed his cell phone up in the space above the tank to get these pics.  All three lines had separated from the tank at the point of joining.  

The first obvious questions are as follows:

(1)  What the heck happened here?  

We cannot tell, other than to note that the the entire plumbing system appears to be ABS DWV pipe with solid fittings and no visible means of shock absorption designed into it.  We bought our AI second-hand, but it bears no evidence that we can find of rough handling or prior damage that might have resulted from an accident (and gosh knows we've crawled under the thing enough to know).  Upon removing the tank (I will get to that in our next post), I did note that the different break points had variable degrees of "dirty-ness" to them, suggesting that all three breaks did not happen at the same time or during a single event.  More likely, these failures were gradual and progressive.  I suspect that the repeated vibration and bouncing from normal road driving simply led to eventual breakage in a system that had no "give" in it, no way to otherwise absorb those applied forces except by breakage.

(2) How many Interstates does this (or will this) problem affect?

We have no idea, but we do know that we are not the only AI owners who have encountered this problem.  This thread on Sprinter-Forum describes exactly the same problem, although maybe not as advanced as in our case (that user maybe appeared to be dealing with partial rather than full pipe separation from his tank).

(3) What's the best way to fix it?

We can't say for sure, but we decided that we would DIY this one for a very simple reason - we were afraid that if we took it to a shop for repairs, we might end up with much the very same type of standard inflexible joinery that would proceed to fail a second time.  Therefore, we had to come up with a re-design that would be more robust, because we do not want to have to fix this twice.

If you are an Interstate owner with this problem, we do recommend that you get it fixed one way or another (either via DIY or by contracting with a vendor who is skilled in RV plumbing).  This system doesn't have a design contingency for chronic leakage.  There are no drain holes in the bottom of the heat shield, so leaked grey water tends to exit from the bracket and all-thread openings in the shield, corroding the sheet metal of the shield as well as the metal support structures themselves.  Even if you have just a small leak from a cracked pipe connection, left unattended it will make a bigger mess over time because of the extra corrosion it will probably cause.

In our next series of posts, we'll provide step-by-step instructions as to how we developed a gray water fix for our Interstate.

Edit 20170702:  Here is the corresponding Air Forums thread.

It's like everything else - it tends to be easy only in retrospect after you have scaled the learning curve.