Black tank - dump valve and rinse connection

[aknavy]

I currently have two issues with my black tank.


The dump valve leaks. There's resistance closing it, and it has a slow leak. Currently have an external valve to ensure I don't take a bath, but need to fix. What are the chances it's the cable routing and not the actual valve? Any tips on replacing the valve from those that have done it?


The black tank flush quite working awhile ago - won't accept water. I've tried using compressed air to blow out any blockage to no avail. Is there a valve in the water line that may be bad, preventing water from going to the tank? Or should I order a new assembly and replace while doing the valve?



Thanks!

[dieselguy]

I'd guess it's the valve itself … common issue after a few years. After being sure the tank is empty and dropping the belly pan in that area, it's 4 bolts to get the valve blade out. A new valve blade with (preferably) a solid wire cable will bolt back in the existing flanges that are glued to the tank outlet and down plumbing. My black tank started leaking on a trip and it turned out to be a stuck piece of wood the factory installer sawed thru the floor and tank top then just let drop into the tank when he was doing the plumbing.
As for the tank flush, there sometimes is a backflow preventer right at the hose connection, but I would think compressed air would have blown it open if it were stuck. Something easier diagnosed while you have part of the belly down fixing the valve.

[cavie]

Originally Posted by aknavy

I currently have two issues with my black tank.


The dump valve leaks. There's resistance closing it, and it has a slow leak. Currently have an external valve to ensure I don't take a bath, but need to fix. What are the chances it's the cable routing and not the actual valve? Any tips on replacing the valve from those that have done it?


The black tank flush quite working awhile ago - won't accept water. I've tried using compressed air to blow out any blockage to no avail. Is there a valve in the water line that may be bad, preventing water from going to the tank? Or should I order a new assembly and replace while doing the valve?

Thanks!

After you have completely drained the black tank, remove the dump hose and use a garden hose and flush the valve and plumbing with the garden hose shove it in all the way to the valve if you can. Exercise the gate valve while the hose in there. You may have TP trapped in the gate slide grove.

[florabama]

The black tank flush uses a check valve which is located up above the wet closet; mine is under the bath sinks. That valve may be bad. Here is a photo of mine.

[CC75]

Originally Posted by florabama

The black tank flush uses a check valve which is located up above the wet closet; mine is under the bath sinks. That valve may be bad. Here is a photo of mine.

My check valve was under the sink in the bathroom. I replaced it with this one: JR Products 571-VAC-CHK-A Vacuum Breaker/Check Valve

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Not to hijack this thread, I do not use a water pressure regulator when flushing the black tank and have wondered if high water pressure could have damaged the valve.

[chaps2018]

The valve is easy to replace. Get the Valera parts from amazon. My experience was not the valve but rather the cable was stiff/needed lubing and there was debris as noted above. I also started to add valve lube (thetford) to the tank. The biggest challenge is getting the tank empty and getting access to the valve.

Thanks for the link. I too use a pressure regulator as one time I had a leak from the Area where that valve is located when we had extremely high water pressure at the campground

[aknavy]

I'll look for that valve - I saw one similar behind the medicine cabinet in the bathroom, but will check in the wet bay as well. Thanks for the info!

[Fifth Wheelers]

If the valve is more than two years old I would replace it, the black tank valve gets used the most and wears out quicker than the others. They are not that expensive.


My black water tank flush had the back flow preventer right behind the hose connection. My line went directly into the tank with a spray head attached in the tank. Not sure why it would go under a counter. I installed a third-party flush system into a friends M/H awhile back and the preventer was part of the water hose connector. Good luck...

[dieselguy]

Fifth Wheelers … the reason some are referring to the flush line going under a counter or under a sink is that many RV's today with the tank flush have a vacuum breaker valve inline somewhere instead of a check valve at the inlet that I mentioned. It's higher than the highest point of the flush line and serves in place of the check at the inlet. All 3 of my Montanas had one. When they fail, it makes a soggy mess as water pours out of the vac breaker fitting while the flush line is pressurized. Been there and have the T shirt … Ha!

[aknavy]

Plan on replacing the flush (in tank portion) and the valve. Guy at the parts store recommended using petroleum jelly on the valve seal when installing. Is that a good idea, or is there a better lubricant for it?

[bubbles]

The rubber seals, 2 each (gaskets) for the plastic gate valve can be replaced separately without (purchasing) changing the complete valve. As said does sound like something is stuck in the gate valve (round plastic slider) groove not allowing complete closure. Of course, the complete valve is not that expensive and easy to change. As far as black tank flush, there will be a vacuum breaker/check valve somewhere inside the unit routed at least above the rim of the toilet. Exact location (under vanity/closet etc.) is a crap shoot. Does sound like the nozzle in the tank is clogged though.

[Rich5117]

Let's hope you will not need to replace the entire valve. Our 2016 Silverback developed the exact same problem. I actually posted about this over a year ago. Our unit came with the Bristol valves and cables. The cables are stranded wire, much like a bike break cable. When I got everything removed and got to the valve I could see that do to usage the stranded cable had twisted and collapsed on its self right at the valve. It broke right at the collapsed area. What I found was that the black tank valve moved freely once the cable was removed and did close completely. I replaced the Bristol cable with a Valterra solid cable. No problems since.

Just recently had to replace the 1 1/2 inch bath valve. This was a completely different problem. When installed the valve was tilted down around the 8 o'clock position and over time water drained into the main valve assembly and caused it to become hard to move in any direction. Replaced entire assembly with a new Valterra valve and cable, also replaced and repositioned both valve flanges so the valve points up to the 10 o'clock position, hopefully eliminating the original porblem.

On both of these valve issues I found both cables were much longer than needed and shortened both over 2 feet.

Hope your repair goes well. Good luck.

[aknavy]

Well, got it all done today. The most difficult part was getting the new valve in and keeping the seals in place while doing it. The old valve had something blocking it - it was 1/4 inch from closing all the way, which left an 1/8th inch gap at the end for the leak. When I inspected it after, I didn't see anything in it. The seals fell out while I was removing the valve, so I suspect that one of them was stuck in it.


Lesson learned - dump all tanks before starting. Would have been much easier if I could have loosened the grey valve above the black, as that would have allowed me to pull the pipes apart. Then it would have been really quick. I ended up using a piece of 2x4 to wedge the drain pipes apart and allow me to get the new one in without screwing up the seals.


I was going to replace the black flush with a Tornado...until I realized that I had to enlarge the hole quite a bit, and it's pretty inaccessible. On to plan B.


Took the original flush out, and it was clogged. It resembles a stationary sprinkler head. I cleaned it up, then drilled all the holes out with a small drill bit. Also added some, as they were a little sparse. I'm not sure it's a great solution, but the reviews on the Tornado are so so. It'll get the job done. Hardest part of that was getting the screws back in - it's a tight space.



The new black valve has a solid cable, and it is easy and smooth. Maybe in the future I'll replace the other two cables, but they work for now.

[aknavy]

Tested out the newly revised flush this morning - way better performance than before it clogged up. When I turned the water on, I could here the water jets inside hitting the far side of the tank. After a couple test fills/dumps to ensure no leaks, my back tank sensor is at the very elusive "empty" light. That'll last till someone used the toilet, but it's a first in a long time for me.

[5picker]

Originally Posted by aknavy

Tested out the newly revised flush this morning - way better performance than before it clogged up. When I turned the water on, I could here the water jets inside hitting the far side of the tank. After a couple test fills/dumps to ensure no leaks, my back tank sensor is at the very elusive "empty" light. That'll last till someone used the toilet, but it's a first in a long time for me.

Thanks for reporting back and great job!

[chaps2018]

Thanks for the update. Can you share the info on the new valve/cable assembly you used in this job?

[aknavy]

Originally Posted by chaps2018

Thanks for the update. Can you share the info on the new valve/cable assembly you used in this job?

I used this one:


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


I'm sure you could just order the seals, if you wanted - it's the same valve as the original, just different cable/cable attachment method.


I took the old cable out and routed this one to the same spot in the wet bay. Cable length is perfect to meet the recommended installation parameters, and is really smooth and easy to operate.



While under there, the flush is pretty easy to get out, and drilling out the holes and adding some made a big difference in performance.

[aknavy]

If anyone is wondering what fixing it involves - this is on our Cedar Creek. All the black/grey valves are in the same spot, only difference in replacing a grey would be the valve size and pipe it's attached to.

https://www.youtube.com/watch?v=VnPx...xtno4rk0h00410