Black Tank flush not working

[DRBusse]

We have a 2022 Globetrotter 25FBT. We have never been able to get the black water flush system to work. On our previous Airstream you could hear the water spraying inside the tank when you turned on the hose attached to the flush input. No such sound and apparently no water going into the tank at all.

We are on an extended stay in NW Montana with no dealer handy, so will take to a dealer in SouCal for warranty work when we relocate for the winter. In the interim, I have had good luck flushing the system thru the toilet or back flowing thru the black tank drain.

Is there a check valve in this system that I am unaware of? Anybody had the same issue?

[pcskier]

There is an antisiphon valve inside the trailer. You can usually find it somewhere behind a sink base in the inside opposite where the exterior flush inlet is. Might be installed backwards, which is the type of thing Airstream seems to do frequently. Or it might be faulty and stuck closed. It will look like one of these attached photos.

[Al and Missy]

Peter beat me to it....


In my trailer there is a combination check valve/vacuum breaker in the line. It is located under the bathroom sink, back against the outside wall. It is similar to this:

https://www.etrailer.com/question-355034.html. Scrll down to see a picture of the valve.

The horizontal connection (the one with the spring in it) is the check valve and should be connected to the tank. If the valve were connected backwards, the check valve would prevent any water flowing into the tank.

[DRBusse]

Update. Dealer replaced check valve and still no water to the spray head. They dropped the black tank and found that the pipe for the flush system was crimped--apparently something that happened during manufacture or initial transport. All covered by warranty. Works fine now.