2011 Passport black tank flush clogged?

[macminn18]

We bought a used 2011 Passport TT. We've been out a few times now, like it a lot. This week we had a full hookup campsite. We thought we would flush the black tank. Emptied the tank, left the valve open, hooked up a hose to the black tank flush, and no water is going into the tank. I'm not sure how it's setup in this rig. Am assuming it's clogged? If I take the external flush hookup, can I access the sprayer or whatever is in the black tank from there?

[JRTJH]

No, you can't access the "in tank spray head" from the outside. The way the tank flush system is constructed, there is a 1/2" PEX tube that runs from the outside connection (where you hook up the hose) to a "anti-siphon valve" (usually located under the bathroom sink) and from there, another 1/2" PEX tube runs to the black tank where it connects to the spray head on the outside wall of the black tank. It sounds like you've never used the system and don't know if it has ever worked or not. There are several possible problems. First I'd suspect that the anti-siphon valve may be installed backwards. Locate it, unscrew it, turn it around and reinstall it. Try the water at very low pressure. If it works, make sure you don't have leaks and then proceed to flush your black tank. ALWAYS USE A PRESSURE REGULATOR WITH THE SYSTEM!!!

If that doesn't work, the next potential problem is tissue and "black tank gunk" dried around the spray head, effectively clogging it and preventing water from flowing through the holes. The "fix" is to fill the black tank with water, let it sit for several days and hope that it softens the "gunk". Then empty the black tank and try the system to see if it will push water through the holes and clear the clog.

The third is a mechanical blockage in one of the PEX tubes. If the system has never worked, it's possible that during installation one of the PEX tubes was crimped and is preventing water flow through the system. You'll have to remove the bottom lining of the trailer to visually check for crimps. I'd exhaust all other possibilities before considering this problem. Chances are it's not this since most people would have noticed the problem and had it repaired during the warranty. PEX doesn't "just crimp" at any given time, so it if ever worked, it's probably not crimped now.

Let us know what you find and good luck....

[JRTJH]

Here are pictures of the black tank flush and a block diagram of the entire system. Hopefully they will help you identify the components and where they are located. The anti-siphon valve is usually under the bathroom sink, way up high, tucked in next to the faucet connections.

[macminn18]

Thank you both for the great info. I did stumble on the anti-siphon valve st after posting. You are correct, we're not sure if it ever was working. Not easy to get to. While trying to diagnose it, I had my DA turn the water on and off to see if it would unclog if that was the problem. Still nothing, but did notice water leaking slowly on the floor inside the cabinet. Hard to tell where it was coming from. The connection from the outside to the inside tube wasn't real tight, so tightened that a bit. But could it have been the anti-siphon valve?

It's my last night of vacation, so am done diagnosing it until we get home.

This forum is incredible for newbies like us, thank you so much for the great info.