2016 Sprinter 319MKS Black Tank Flush System

[Sigohigo]

We have a new TT that has already been in for warranty work to fix the black tank flush system. However, after having just returned from our second trip it has to go back to the shop as no water will pass from the outside connection to the inside of the black tank. Same issue that was supposedly resolved by the selling dealer. Any ideas as to why I am having this problem?

[sourdough]

to the forum. There are several threads pertaining to your issue if you use the search function. Mine didn't work and they had to repair the "backflow valve?". Others on here have a lot more experience and detail on the subject. I would suggest in the future when you have repairs made you do a walkthrough with the tech/service advisor/service manager and make sure the things you wanted corrected are indeed corrected. This particular issue should have been caught on the initial PDI.

[therink]

Yes, the inline backflow preventer was likely installed backward for m the factory so the flow is the wrong way. It is easy to change out. If your dealer couldn't identify and fix this the first time, I wouldn't even bring it back or trust them with my rig.
The backflow preventer would normally be located just inside the exterior wall in line where the outside flusher water hook up is. It is usually in a cabinet, under a sink or such, usually in the bathroom. It will extend up a foot or two above the floor. It is a $15 part and can be purchased at home store if needed.

[Sigohigo]

Agree with both of you. I am taking the rig back to the dealer tomorrow to give them one last try. There are other Keystone dealers closer but you would think the one you buy it from would want to service it for you.

I will check under the bathroom cabinet tonight to see if I can see the back flow valve. I never thought about it but it makes sense.

[rntacp]

Likely to late but you can just replace the valve yourself and save yourself a trip to the dealer. This forum is a wealth of knowledge. First thing I did with my new Hideout last year was take that POS back flow valve out from under the sink. I made my own out of brass fittings from the local plumbing store. Two brass connectors, a one way valve and a lot of plumbers tape. I know a lot of ppl don't like plastic to brass fittings but if you're careful and don't over tighten its fine IMO. It's a far better solution then another plastic valve that may fail especially after winterizing. Mine worked great, opened up the trailer this year and zero issues.