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Topic: Black tank mystery (Read 1879 times) previous topic - next topic

Black tank mystery

This winter I fulltimed in northern New Mexico. In January my tanks, or at least some part of tanks froze up and I put an electric heater on top of battery bank cover facing the tank exit area. After a bit I was able to drain the gray tank but not the black. I moved out of RV for couple months and  Now I am back to working on it. I purchased TankTechs Rv, all natural probiotic tank treatment and waited but no change.

When I click on button to open the black tank and drain it, the lever seems to make the same noise it ever did that accompanied the opening of that tank and I can see the lever opening upwards but nothing comes out.

Today I put a small 20 foot "snake" down toilet but came to no blockage that I could tell.

Any ideas?

Re: Black tank mystery

Reply #1 –
If you pour a cup of water down the John does anything comes out?

Re: Black tank mystery

Reply #2 –
Andy2,

To clarify your question do you mean does anything come out the drain if I pour a cup of water into toilet?

Re: Black tank mystery

Reply #3 –
Also, the black tank is so full I can see liquid about 7 inches down the toilet just before the pipe turns. So I hesitate putting much liquid down there.

Re: Black tank mystery

Reply #4 –
Quote from: Susan –
Today I put a small 20 foot "snake" down toilet but came to no blockage that I could tell. U
Any ideas?

In your (our) situation a 20' snake isn't really small.  It's long enough that it can easily coil up in the tank and never find the drain opening.  I would try running the snake in from the outside by punching a hole (no bigger than the size  of the snake) in the sewer line nearest the valve and see if you can clear the clog, or run into the unopened valve blade.

Re: Black tank mystery

Reply #5 –
I have a few ideas but they all end badly... :))  :-X 

Take a hose and wrap it with a wet towel in the drain pipe.. wrap it tight and turn the water on..Pressure should get it to release.. possibly ... Told you I had ideas...

Re: Black tank mystery

Reply #6 –
Thanks David and Traveling man. Getting dark and cold now. Will try your ideas in morning!

Re: Black tank mystery

Reply #7 –
This is what I would try, I've used one for over 10 yrs to back flush.  Just be careful not to overflow black tank.

Flush King RV Holding Tank Flush Valve - YouTube

Also I would try both of these companies products after you get the clog or cone out, first their Extreme Cleaner and second their regular product which I also have used for over 10 yrs.   

Home - HAPPY CAMPERS 

Flush King | Camping World

Re: Black tank mystery

Reply #8 –
If your snake has a few bigger coils on the end then you can make a hole in the sewer hose big enough to accomodate it then once inside wrap duct tape around the hose to reduce the opening size making it tight.  Make the hole on the top of the hose in case you get lucky and the dam bursts.  Good luck.

Re: Black tank mystery

Reply #9 –
Maybe try this.  Put a ladder next to the tank, then hookup your sewer hose and duct tape the other end so that it is higher than the top of the tank.  Then open valve and run the snake down the hose into the tank.  Hopefully once it breaks up the blockage, pull out the snake, then you can either dump or close the valve and drain the hose into a container for disposal.

Re: Black tank mystery

Reply #10 –
Quote from: Susan –
When I click on button to open the black tank and drain it, the lever seems to make the same noise it ever did that accompanied the opening of that tank and I can see the lever opening upwards but nothing comes out.
This sounds like you have some kind of electric tank valve.  Is that correct?  If you can see the "lever" moving, but nothing comes out the drain, then it is possible something in the connection between the lever and the actual gate valve has come loose or broken.

Do you have access to the valve, where you could see to work on it?  If you can see what part of the linkage is broken, you might be able to open the valve manually.

Regular manual dump valves are just a simple sliding gate that is pulled up by a threaded rod to open the valve.  If my guess about "the problem" is correct, then you just need to figure out how to grab hold of the top of the sliding gate and pull it up.

Sorry - without some photos it is hard to visualize exactly how you would do that.

Re: Black tank mystery

Reply #11 –
These valves are known to fail by the shaft pulling out of the gate/guillotine, it appears to be opening because the shaft moves, when in fact the valve part didn't move. I would think this would be more likely than a watertight clog.

Re: Black tank mystery

Reply #12 –
FOT replaced our black tank valve when we were there last. It had gotten so stiff that I once actually broke the handle trying to close it.

You're a bit too far for me to drive there and help, but can you take off the panel in the wet bay that covers the actual valves? It will take some work, but it is pretty straight forward. Once you get that panel off, and can see the valves, you ought to be able to see if the valve is actually opening. The rod may run through one or more supports, so that it doesn't flex when you push it closed. Those supports may make it seem like it is operating normally, when in fact it isn't.

Re: Black tank mystery

Reply #13 –
I found a good thread over at the Airstream forum - shows a very good example of a similar problem, where the rod pulled out of the "blade".  I'm glad I did this search and found that thread.  I now have a much better idea of how the valve is assembled and how it operates.  If I ever run into this problem (and I probably will) it won't be nearly as intimidating.

The owner had to actually remove part of the upper valve housing with a Dremel tool so he could grab the blade with Vise Grips.  This would be one possible solution to a disconnected valve blade, IF THIS IS IN FACT THE OP's PROBLEM.

Waste valve handle and rod pulled out of the valve - Airstream Forums

Re: Black tank mystery

Reply #14 –
Kinda what I was thinking .. once he tried the water the opposite direction I think things will be clearer,, No Pun intended!! ^.^d

Re: Black tank mystery

Reply #15 –
If---IF---you are sure your valve is opening and closing correctly, and the tank is NOT frozen you might try some light percussion persuasion on the area closest to the shutoff valve and the tank.
Just light taps as far around as you can go and attain some vibration without breaking the plastic.
Have your slinky hooked up and the valve open and the other end of the slinky pointed in a safe direction, preferably down the dump input.
It can take an unbelievable amount of time to thaw the black tank to the point that it will flow.
I would even go so far as to put a bunch of De-icer down the toilet.
I currently have a leanto with a dirt floor and the water/ice is still froze after everything outside has thawed and drained away, so I know it seems like forever before the ice melts.

Re: Black tank mystery

Reply #16 –
If you think your tank is still frozen, put some coarse salt down the toilet and let it melt the ice. Just a thought.

Re: Black tank mystery

Reply #17 –
I agree with Chuck, sounds like something has become disconnected. My manual handle broke off and had to replace entire valve. Had to dremel cut away part of the housing to be able to grab the blade with needle nose pliers. Wrapped towels around the valve when pulling the blade. I didn't use quite enough towels tight enough. Had liquid seepage for a couple of minutes till drained. After empty, replacement was straight forward. I did remove a section of the hard plastic drain pipe and replaced it with a flexible rubber hose and clamps to give enough room to remove the old valve and rusted bolts. Next time, the removal will be much simpler. I did a post with pictures on this about 3 years ago. I would try the snake up the hose to see if I could hear it hit the valve assembly. On my coach, this would only be about 3'.

Hope it is a simple fix.
Larry

Re: Black tank mystery

Reply #18 –
I unscrewed the little "wall" that was in front of the gates. First photo closed. Second photo open.

Hope they aren't too dark.

Re: Black tank mystery

Reply #19 –
Need to make sure the flange is moving.. Is it still frozen or are you in a warmer location?

Pics kinda dark