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Old 11-17-2019, 11:37 AM   #1
New Member
2014 Interstate Ext. Coach
Virginia Beach , Virginia
Join Date: Nov 2019
Posts: 2
Black tank dumping problem


Just registered on this forum after finding it to be a very useful resource in learning about my new-to-me 2014.5 AI EXT. Many thanks to the participants of this very knowledgeable and helpful community !

In preparing for my first trip (heading to NM first week of December), I've been testing out all the systems. Everything seemed to be working as expected until I got to dumping and flushing the black tank. The on-board tank monitor indicated that the black tank was empty or near empty. When I opened the dump valve and turned on the macerator, almost nothing came out. Here is where things started to get interesting. I wanted to use the black tank flush inlet located next to the dump hose, but when I connected the flush hose, water would not enter into the black tank. I have read on this forum that a likely culprit is an improperly installed check valve. I will have that checked out, but if there is anything else I should check, please let me know.

Since I couldn't fill the black tank this way, I decided to just let the toilet run so that the water from the fresh tank would fill the black tank. When the tank monitor indicated that the black tank was between 2/3 and full, I went outside to dump the black tank. Here is where the second unexpected issue came up. As soon as the black tank valve opened, I heard a rush of water under the coach. Peeking below, I could see water pouring out of the bottom of the coach onto the pavement. Luckily there was no sewage in the tank, but it still created a big cleanup headache as I had to sweep the water into the drain and hose down the pavement.

So, I would like some guidance as to what I should do next, particularly about the second issue. I've done searches online for this and I haven't had any luck coming across anyone describing such a problem with their AI black tank. FWIW, grey tank flush went without incident. Apologies in advance if I haven't included all the relevant troubleshooting info. I'm still quite new at this, so learning as I go.

Thank you in advance,

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Old 11-17-2019, 01:31 PM   #2
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Pahaska's Avatar
2018 Interstate Grand Tour Ext
Austin (Hays County) , Texas
Join Date: Jun 2002
Posts: 7,164
Images: 4
Something may have struck the PVC plumbing under the coach. It is quite low. A road alligator can do damage. Mercedes broke mine while putting the AI on a lift when they left one of the lift parts in the wrong place.
John W. Irwin
2018 Interstate GT, "Sabre-Dog V"
WBCCI #9632
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Old 11-21-2019, 06:42 PM   #3
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1992 29' Excella
2010 22' Interstate
Van By The River , Georgia
Join Date: Feb 2002
Posts: 2,251
Hello TribeFan,

Welcome to Air Forums. As you've found, this web site is a wealth of information. Keep in mind that almost every year there are changes to Interstate vans so you van is very likely different than our 2010 van. I helped somebody with their valves on the waste tanks and their plumbing arrangement was entirely different than ours. I guess what I'm saying is... it's very difficult to comment on details without pictures or some additional information.

Where did the water leak from? Is it a gaping hole? Broken pipe, broken or disconnected flexible pipe? There are several places that water may leak. You will need to put your van onto some wood ramps so you can get under there to do some more checking.

The van is very heavy so the ramps must be solid wood. Our ramps are constructed of 3 pieces of 2 X 8 layered on a piece of plywood and then layered again with 2 X 8's. We get about 4" of lift by driving onto the ramps. This allows me to wiggle under the van to look at components in more detail.
Lucius and Danielle
1992 29' Excella Classic / 2010 Interstate
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 11-23-2019, 06:07 AM   #4
Rivet Master
2013 Interstate Coach
Raymond , Iowa
Join Date: Jun 2014
Posts: 1,512
As stated above we need to know where the leak occurred in order to help solve it. Since it is just associated with the black tank, start at the black tank valve and work you way upstream. Pretty shabby for it to have been sold to you with this problem (which may or may not be hard to fix).
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Old 11-25-2019, 04:45 PM   #5
New Member
2014 Interstate Ext. Coach
Virginia Beach , Virginia
Join Date: Nov 2019
Posts: 2
Thanks to all who replied with suggestions. I don’t have a ramp or proper materials on hand to safely build one, and being inexperienced with RVs, I decided the most prudent course of action was to take it to a local RV service shop. They were able to lift the rig and inspect the underside, revealing a broken fitting which caused the leak. Took less than 30 min for them to fix, and I am now ready to go! Thanks again!
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Old 11-26-2019, 09:04 AM   #6
1 Rivet Member
2015 Interstate Grand Tour
Cedar Park , Texas
Join Date: Jan 2016
Posts: 15
Had similar issue. In my case the clamps had worked loose on the black tank tubing were it connected to the pump system.. I reset the tubes and relighted the clamps and issue has resolved.
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