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Old 06-22-2022, 06:23 AM   #1
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Join Date: Apr 2018
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M.O.C. #21600
Black Tank Valves

Hello everyone,

I've been a member for a long time and find these forums helpful, but this is my first question to the group. We have a 2015 3625RE that we bought new in 2015. We just started full time while we build a new house, in south Georgia, in the hottest June on record. It will be 104 today.

Anyway, at Christmas when we spent 2 weeks in Panama City Beach, I found that the black tank operating valve was very stiff. I took the cable out of it's mounting hole and sprayed lube down the cable and that freed it up and operation seemed normal, but I think at some point it had stopped sealing the tank completely. Now, the tank is filling up very quickly, so I assume I have a pyramid built up.

I have 2 Valterra valves with cables on order and due here Thursday. My question to the group is 1) has anyone else had this issue? and 2) what did you do to break down the pyramid after the valve situation was resolved?

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Old 06-22-2022, 06:39 AM   #2
Seasoned Camper
Join Date: Mar 2018
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M.O.C. #21318
I have used this for awhile and I have heard good things about it helping with a pyramid. My personal experience has been after the first 3-4 times using this that it seems my tank cleans out quickly now when I am flushing it out. Hope this helps.
Wayne & Joyce
2021 Montana 3781RL
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Old 06-22-2022, 07:26 AM   #3
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M.O.C. #12156
I have used various septic products over the years, has never damaged anything. Fill the tank three quarters and let the product sit Get an external sewer pipe valve that allows you to backflush, much better than the OEM backflush. Mine is called Super King. Valterra makes one as well. Available anywhere RV parts are sold. Run a hose into the toilet and run water into the tank from the top while at the same time backflush with the external valve. Just be careful of overfilling. The one I have allows connection of a hose, I run a second hose from the water source and just leave it connected. I use that to backflush each time I dump either black tank. Using that backflush process I have not any buildup in years. I got tired of the cables, did some minor reroute of my pipes, and have direct threaded rods for valve operation.
Mike and Lorraine
2002 3655 FL, 2005 3650RK
2010 3665RE, 2015 3910FB
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Old 06-22-2022, 08:06 AM   #4
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I use a Valtera valve at the dump port (one valve stops all 3 tanks on our rig). We leave open when connected to sewer and keep galley tank open. When dumping black tank I close galley and dump black, then I close the dump valve and open bath grey (while black is open). Once the grey flushes back into the black (you can hear the flow stop) I close the grey and reopen the dump valve. Thos process gives quite a backflush thru the black tank valve and, in theory, attacks any pyramid from a side/bottom direction. With clear fitting at the dump valve I'm able to see the amount of additional stuff that the grey water backflush brings out of the "empty" black tank. Once that drains I close the black, close the dump and open the grey again. The second "whoosh " from the grey fills/flushes the tank drain pipes and then I open the dump and let the grey complete draining. Close grey and open galley again.

I will rinse black every other dump using the rinse port, but before I started using method above I rinsed every dump and still had worthless gauges (black and grey). Tried tank and gauge cleaner in both tanks but still no luck on our gauges.

We also use products that introduce aerobic bacteria into the tanks. These products work better when tanks aren't completely drained after each dump, but I figure we never get them completely empty. Have always have good results with them on our boat(s).
Rip & Beth
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Old 06-22-2022, 01:15 PM   #5
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Do an black tank flush
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Old 06-23-2022, 04:24 AM   #6
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M.O.C. #25165
Black Tank Flush with Unique Digest It. Let is sit overnight, then flush well again with plenty of water. If you are still getting water and waste past the valve, there may be some paper or waste blocking the valve from closing. Flushing thoroughly should get it cleared.
Robert & Diana McNeal
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Old 06-23-2022, 08:28 AM   #7
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I've always been known as someone who likes to stir s*** up, so it was easy for me to use a 1x2 down the toilet, and stir it around while running the flush water. My problem is a very sticky valve that probably has a wipe wedged in the valve slot, which I can't shut completely, allowing the liquid to drain constantly. As I'm sitting here in the RV typing this, I'm thinking about the replacement valve waiting for me in the storage compartment.
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Old 06-23-2022, 08:53 AM   #8
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If there is 'crud' on the black tank dump valve itself, then there is still something you can try before dismanteling anything. As stated above, block off the end of the dump pipe with another valve, like a Flush King or as mentioned above the Super King. Close this valve and leave the black tank valve open. Now add some water, enough so it will fill the outlet pipe and cover the black tank slider valve. Also add some enzyme eaters, Rid-X, septic tank booster, or something like was mentioned above. Let THAT sit in your pipes, covering the valve and lit the enzyme eaters dissolve whatever is clinging to the valve. Do this first and give it a chance to work so you don't have to tear your trailer apart (yet). Start simple, and work for a more complex solution when the simple does not complete the mission at hand.
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Old 06-23-2022, 08:56 AM   #9
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It might be worth mentioning that the pyramid forms primarily from leaving the black tank dump valve open, which causes the liquid to drain but not the solid contents. This could also be a source of the difficulty in moving the valve. The suggestion by others to use either Tanktechsģ or Unique Digest itģ products left in a full tank of water for a day or two, then dumping is a very good one!! A flexible flushing wand inserted through the toilet would also be a worthwhile try in conjunction with the after soaking dump.
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Old 06-26-2022, 02:14 PM   #10
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I do the same as RipNC. 2014 model and in 8 years I have replaced 3 valves so using the one "main" add on valve and backflushing is working well. We FT for 5 year in that period and now are 6 months in/ 6 months home so it gets a lot of use. No build up.
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Old 06-26-2022, 04:07 PM   #11
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Originally Posted by RMcNeal View Post
Black Tank Flush with Unique Digest It. Let is sit overnight, then flush well again with plenty of water. If you are still getting water and waste past the valve, there may be some paper or waste blocking the valve from closing. Flushing thoroughly should get it cleared.
Agree with RMcNeal!! UNIQUE digest it is a live microbial tank treatment. I would add that you might want to let it sit closer to 24 hours depending on the blockage. Read the instructions and add more than normal amount. Fill your tank at least 3/4 full . The instructions say NOT to flush your tank, just empty as normal. Add about 4gal fresh water and another dose of the product and you should be good to go. I only do a good flush when Iím going to but the rig in storage. I still add 4gal back in, and some product, and put the rig away till next time we go on a trip. There is also a valve lube available that you add to your tank and it seems to work well for me. My valve seemed hard to open and close when I first got it. Added the valve lube. Flushed the tank and worked the valve a few times and it loosened right up. Both products available on Amazon, and probably Walmart as well. Hope this helps.
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