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Old 11-06-2015, 08:13 PM   #1
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2014 27' Flying Cloud
2016 Interstate Grand Tour Ext
Merritt Island , Florida
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2016 Interstate black tank flushing

We just completed our first shake down cruise and find an unusual problem with the black tank flushing during sewer dumping. Using a conventional "Y", one hose connects city water while the other will flush the black tank. If the city water is still connected and pressurized, everything is fine. If the city water is turned off to the van when the flush is turned on, then lots of water spills into the inside wall of this Grand Tour, behind the reefer. While it can't be seen, it can be touched and seems like the water pressure regulator. No water actually goes into the black tank and water goes everywhere inside the drivers side wall. The manual does not specify that city water must be connected and pressurized for the flush to work.
Anyone have info?
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Old 11-06-2015, 08:42 PM   #2
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2016 Interstate black tank flushing

Quite a bit doesn't make sense to me:
Firstly the hosepipe used for flushing the black tank should never be the one you use to connect to city water or to fill the fresh water tank. This is because back flow from the black tank can contaminate the hosepipe. So using some sort of Y-fitting on a single hosepipe to perform both functions is a no-no.
Secondly, the black tank flush is located under the van below floor level, so I cannot see how that can flood any part of the interior. However, there may be a chance of overflowing the black tank if you leave the flush on for too long, and if there's a bad seal somewhere below the toilet, it may leak inside, but that's likely to be in or around the bathroom area.



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Old 11-06-2015, 09:37 PM   #3
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The flush line has an air gap fitting behind the refrigerator. The fitting was installed upside down in my 2015 Grand Tour. The air gap fitting needs to be rotated to keep the water from falling out.
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Old 11-06-2015, 09:41 PM   #4
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Does it leak when you directly connect the flush line without a Y? (And I agree-you shouldn't use a Y).

The only "regulator" is the one that is behind the fresh water inlet. It can leak there if the connector to the water line, which screws on, is loose. It can also leak if the connection has a lot of pressure and is loose as well.

Actually, the black tank flush line goes straight up into the van, then about 18" above the floor, then takes a 90 degree turn into a cheap plastic backflow preventor valve that is screwed on one side and connected with a pex connector on the other, then another 90 degree turn back down to and goes just under the floor, but above the metal van floor, over to the tank.

The backflow preventor valve is screwed on. It likely is not tight or there is s bad connection or defective. You may have to remove an appliance to get to this valve (as I'm not sure of your model).

There is no connection between the black line and the fresh water line. It has no bearing on why or what is leaking.

My guess, if it leaks when you have a hose directly connected to the flush line is a sloppy installation that did not adequately tighten the backflow valve to the line.
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Old 11-06-2015, 09:41 PM   #5
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The flush line has an air gap fitting behind the refrigerator before entering the top of the black tank. The fitting was installed upside down in my 2015 Grand Tour. The air gap fitting needed to be rotated to keep the water from pouring out behind the refrigerator.
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Old 11-06-2015, 09:59 PM   #6
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I guess I should add "or they installed it upside down." But I didn't figure they could be incompetent enough to do that. I should not have made that presumption.

Take it to the dealer and make them fix it under warranty. In the meantime, don't use the flush line if it leaks.
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Old 11-07-2015, 08:05 PM   #7
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Thanks for info. For UKDUDE, perhaps I was not clear. The Y goes on the campground hose bib. A white 25' hose is connected to the Interstate water inlet port. A black hose connected to the other side of the Y goes to the flush.
Normally pressure is present on the white hose and the black hose is opened for a few seconds to flush the black tank. If, however, I just have my garden hose connected to the black flush (no water to Interstate water inlet port), water leaks dramatically from somewhere behind the fridge. I have repeated this. If I use the campground setup - all seems OK. I can't believe the circuits are connected in any way. Maybe the back flow preventer is not installed correctly, but then I can't explain what is happening.
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Old 11-08-2015, 08:47 AM   #8
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I would pull the fridge and try again, but since it's under warranty, take it back to the dealer and have them look.

"Water is never good where it is not supposed to be."
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Old 11-08-2015, 04:59 PM   #9
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Quote:
Originally Posted by Dsquare View Post
No water actually goes into the black tank and water goes everywhere inside the drivers side wall.
My backflow preventer was installed backwards. Since you said no water actually flows into the black tank, I suspect yours might be also. Not sure why that would have any connection to the city water connection and your leak.
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Old 11-08-2015, 09:58 PM   #10
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Hmmmmmm....curious. I have never used the flush connection on my Interstate, but last year during winterizing...I tried to push antifreeze into that port. I blew the hose off and did not get anything to go in. Since I don't use it, I didn't worry anymore. Now you guys have me wondering.
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Old 11-09-2015, 09:10 AM   #11
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wow - same here, never used the backwash connector on my unit (ran a hose into the toilet. Was getting ready to try the flush connector this year, but really don't want to have to pull the fridge and mess with any other fix that the factory should have known better than creating - like many others here - making the 3 hr drive to closest dealer twice (once to drop off, once to pickup) is more of a pain than fixing things myself.

Another 'feature' that I won't be using on my AS.
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Old 11-09-2015, 10:02 AM   #12
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I'm not sure how yours is configured, but for my 2011, I had to remove the microwave, not the fridge, to repair the backflow valve after it broke when I didn't winterize that line (nowhere in the Airstream literature mentioned that, nor did the dealer and I never simply thought about it). Actually, it's not that hard to do with the microwave out, as it's right behind it. But even if you have to remove the fridge, that's quite easy to do as well.

I removed the backflow preventer valve altogether. For it to flow backwards, fluid would first have to climb about a two foot pipe to reach it, and last time I check, gravity flows downhill. There is no possibility fluid could ever flow backwards in the first place. At least they did that right. Now I don't worry about winterizing that line because nothing can stay in it.

If your hose blew off when trying to winterize it, the valve had to be put on backwards. There should be no pressure on that line if the valve is facing the right direction. It's has a simple plastic flapper that opens when fluid flows from one side, and close if it flows from the the other.
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Old 11-09-2015, 01:39 PM   #13
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Ditto the response bygmillerok1 for my 2013. Remove the micro, not the refrigerator. Remove the plastic valve and take it to the hardware store. Buy plastic fittings that assemble into about the same inlet/outlet config as the valve and replace. 30 minute job plus travel time to the hardware.
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Old 11-09-2015, 02:19 PM   #14
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On my 2011, the check valve in the black tank flush line is on the curbside. Need to have the slider fully open to remove the panel to access it.

FWIW, I recommend using the flush line after each pump out. I put a adapter fitting on the outside spray hose (removed the sprayer first) to allow me to do that when no city water available as it usually isn't at the pump out facilities.
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