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Old 06-06-2021, 02:09 PM   #1
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Black Tank Flush question

We are permanently parked at a camp ground so this beast never goes anywhere. How often should I flush the black tank? How much water should I run through it when I flush it out? I have a hose attached to the black tank flush so water is readily available. We are relatively new at this so any suggestions will help. Just dealt with our first "poop pyramid", got that taken care of. Now I just need to know more about the black tank flush! Thanks.
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Old 06-06-2021, 02:28 PM   #2
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I run the black tank flush every time I dump and run water until it mostly comes out clear.
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Old 06-06-2021, 09:14 PM   #3
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I would not be leaving the hose connected to the black flush inlet. By doing that, you are not allowing water between the inlet and the backflow/air gap valve to drain out, which is how that is supposed to do. I drain the black tank once a week and use the flush system each time, and NEVER leave the black tank drain valve open.
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Old 06-07-2021, 06:19 AM   #4
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I run the black tank flush every time I dump. I also back-flush from the grey tank every time I dump. It's just become my normal way of doing it.

We are currently at home (which is a rare event lately), and I broke out the power washer and power washed the neck of the toilet where all that "stuff" seems to stick and dry. While doing so, I shot straight down. If there was any chance of a poop pyramid starting to form, it's gone now! When I while using the pressure washer, I was shocked how dirty the water was, which means, even in our best efforts to add extra water, dump and fill the tank again and dump, back flush, or use the black tank flusher, there is still a LOT of "stuff" that sticks to the inside of those those tanks that never gets completely cleaned out. Of course, we use our camper, pretty much 365 days a year too, even when home.

So, it does not hurt anything to use the black tank flush as often as you want, or back flush, or add extra water, or even power wash the tank out! The cleaner you can keep your tank, the less chance of smells and poop pyramids and toilet paper sticking inside the tank.

And by the way, I advise getting a clear section that attaches to your trailer dump, or a clear elbow that goes in the ground, because if you have never seen what's actually coming out of your tank, even after you've flushed it, you in for a pretty big surprise! You'll flush it a lot more, and a lot more often.
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Old 06-07-2021, 06:35 AM   #5
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I would never use a pressure washer to "clean" the black tank or any other tank on the Montana. Too much pressure could damage them. Use the factory tank wash as much as you want though. Leave black tank closed until ready to dump and won't have pyramid problems.
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Old 06-07-2021, 12:07 PM   #6
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Second Grey tank Clogged

My Montana second grey tank is clogged , water is full and backed up , I pulled the grey tank level in the compartment and the hidden one underneath the living / dinning room slide at the back end of the slide . Still no luck , I used a whole gallon of liquid plumber , and have ordered me some Shock it conditional treatment , hoping it will do the job , can't figure out the problem why .
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Old 06-07-2021, 12:41 PM   #7
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It helps if you tell us what year and model RV you have. But most Montanas use a solid pull rod (rather than a cable) to operate the gate valve on the tank. They are pretty foolproof. It sounds like you have a valve problem (as in it is not opening). Pouring chemicals down the drain is worthless. You need to gain access to the valve and determine why it is not opening.
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Old 06-07-2021, 02:37 PM   #8
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Some of the new high dollar motor homes now have macerators in the toilets, so you can leave the black tank open.
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Old 06-13-2021, 03:59 PM   #9
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Pre-charge holding tank with 15-20 gallons of water metered through tank flush connection with a low cost P3 in-line turbine meter. Dump and flush weekly then pre-charge with 15-20 gallons.
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Old 06-14-2021, 01:13 PM   #10
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When we are parked for a long term, we keep the blank tank valve closed.
Then we we see it close to full, we pull the valve and when emptied, we flush.
I flush it until it becomes "drinkable" ) Not really, but we flush every time we dump.
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Old 06-14-2021, 09:12 PM   #11
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If i was stationary, i would give this a try. Once the tank is conditioned and ecosystem stabilized, you never backwash/flush or drain all the way.

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