Black Tank Flush

[C. Brown]

When I flush my black tank in my 2021 Montana H/C I will dump tank first.
Then I close the valve and flush for 2 minutes, then I dump that. Then I close it off again and flush for 3 minutes and then dump again. I will repeat again for 4 minutes. Am I wasting water because my black tank sensors still do not work? The sensor shows full all the time.

 

[Joe DIrenzi]

Welcome to montana world.I have a 3721rl 2018 and the sensors have read full since day one.

 

[JDDilly]

I am not sure about closing the valve, I never have. I would be afraid of over filling the tank, especially running the flush for 4 minutes. I leave the valve open and run for 3 to 5 minutes. A few times a year, I will fill the tank about 3/4 full when traveling.

After you use the tank, the sensors will not work. Most people never worry about them and dumps the tank when it does a burp like function when you flush (hard to explain, but you will notice it when it happens).

 

[C. Brown]

I am not sure about closing the valve, I never have. I would be afraid of over filling the tank, especially running the flush for 4 minutes. I leave the valve open and run for 3 to 5 minutes. A few times a year, I will fill the tank about 3/4 full when traveling.

After you use the tank, the sensors will not work. Most people never worry about them and dumps the tank when it does a burp like function when you flush (hard to explain, but you will notice it when it happens).

I stand by outside with a timer on my iphone so I do not get distracted and walk off with black tank flush running. Did that one time, not cool!!!!!

 

[mhs4771]

I've go a step further, I use a cheap ($10-15 Buck) inline flow meter. Originally did the timer method, but realized that different places had different flow rates.
So I dump first with the Flusher running, once the flow slows down, close the valve and fill with 30-35 gals (have a 45 Gal tank), open and drain, close and fill again with 40 Gal, drain and them open Grays and while they're draining I fill and flush the toilet approx 3 times, go back outside close the Grays and refill the Black with 45 gals, drain and disconnect the flush line, close everything up and done until the next Burp.
No chems used, just a capful of Calgon and a cup of Dollar Store Pine Sol.

 

[DutchmenSport]

To give your sensors a better chance at working, dump your tank, flush it the best you can. Then add about 4-5 gallons of water, dump a half a cup of Dawn Dishwashing Liquid down the toilet, and drive to your next destination. The sloshing of the soap water will clean the crud hanging on the sensors and they will work again. I've been doing this for over 20 years in 4 different travel trailers and fifth wheel. Mine have always worked.

Now, to aid dumping your black tank? If your grey tank and your black tank join to a single outlet (2 valves), get yourself a Flush King valve and attach it to the drain outlet. Now do the following:

1. Drain the black tank completely and leave the valve open.
2. Close the Flush King valve.
3. Open the grey tank valve. This will now allow water from the grey tank to back-flush with force into the empty black tank.
4. Count to 10 and then close the grey tank valve.
5. Now open the Flush King again and let the black tank drain completely again.

Repeat this process 3 times, or until there is not enough water left in the grey tank to make any difference. What little bit of grey water is left after the 3rd back flush, use it to drain and clean out the sewer hose.

If you can get a clear section of drain so you can see what is actually coming out when you back flush, you'll be very surprised what, and how much more comes out.

NOW!! do a final flush with your black tank rinse and just let it run.

A few things are accomplished by doing this, namely you use MUCH less water to clean out your black tank as you are re-using your grey water instead of just dumping it and then using even more clean fresh water to flush the black tank.

Second, if you dump into a Blue Tote to cart away your waste to the dump station, you are not filling the tote multiple times as you are using only water that needs to be dumped anyway.

Third, back flushing cleans your tank, really well.

Now that you have back flushed, add the water, add the Dawn, and drive to your next destination and dump again. Sensors will work, tank is clean, never have smells or odors, and you've helped save the planet. It's a win-win in every direction to back flush.

 

[glb1950]

Geez I hope you're right about this, I just ordered one on Amazon and will post results here after it arrives. Thanks for the tip. I'm always trying to learn new things.

 

[Lindyn]

I have never payed any attention to the tank sensors. After you live in a RV you will learn when to dump tanks. I also drank black tank first, then I close valve set timer for 8 minutes set time on iPhone, and repeat, Then after flushing I put in about 3 minutes, close valve. Then empty both gray tanks. Works for me. We do know boon docking at all. I had enough camping in my 26+ years of service in the US Army. We are RVer's not campers.

Happy trails.

 

[BB_TX]

.........Am I wasting water because my black tank sensors still do not work? The sensor shows full all the time.

My tank sensors never worked right. I used pretty much the same procedure as you but using a clear extension at the dump pipe. After each closing and opening of the drain valve I would see additional solids come out, each time getting less and less until it is mostly just brown colored water coming out. So no, you are not wasting water. Each cycle gets a little more of the solids out so less to settle and solidify on the bottom of the tank.

 

[Hblick48]

Geez I hope you're right about this, I just ordered one on Amazon and will post results here after it arrives. Thanks for the tip. I'm always trying to learn new things.[/QUOTE

I used ABS cement to glue the vew valve onto the discharge end. Never have a "trickle surprise" when removing end cap.

In addition to using grey water to rinse your black tank, the new valve also allows us to extend boondocking. Shower tank always fills up before galley tank. Close the new valve at the tank discharge point. Then slowly open both grey valves. Grey tanks equalize and become one. Much more room for grey water.

When dumping, close both grey valves. Dump black tank until empty. Use procedure above to use grey water to rinse black.

 

[Daryles]

I also have the Valterra gate valve. I put a 3" clamp around the connector end to prevent it accidentally falling off going down the road.

Hblick48,
It would depend on how your tanks are configured in your rig if this trick of sharing tank space would work.
I have a 3130re. The galley tank is mounted higher in elevation than the bathroom grey or black tanks. Therefore my galley tank will always drain into my grey or black tanks (I do the grey tank backflush trick too).
However, the 3" drain pipe between the tanks to the gate valve will hold about 8 gallons giving you some extra boondocking space for grey water. I wouldn't do it with the black tank.

 

[DutchmenSport]

Ah, it's so nice to read that some other folks also back-flush and actually see the value of it. Far to many times (on different forum sites), I get heckled because folks just don't think it benefits anything, that their tanks get cleaned out by simply doing a one time dump with "plenty of water."

!

 

[glb1950]

Hence the reason I'm on this forum. Pick the brains clean of all useful information from more knowledgable people than myself.......before I destroy everything trying to do it my way.(usually the wrong way) Thank you

 

[C. Brown]

I am not sure about closing the valve, I never have. I would be afraid of over filling the tank, especially running the flush for 4 minutes. I leave the valve open and run for 3 to 5 minutes. A few times a year, I will fill the tank about 3/4 full when traveling.

After you use the tank, the sensors will not work. Most people never worry about them and dumps the tank when it does a burp like function when you flush (hard to explain, but you will notice it when it happens).

Have you ever tried putting a cup of Blue Dawn dish washing liquid in it when traveling to clean it?

 

[CaptnJohn]

OP has a good method for back flush, there is only ONE way to eliminate the frustration and aggrivation of reading the sensors~~ I realized this decades ago,,, PRETEND THEY DO NOT EXIST!!

 

[Montana Man-MOC]

I have never payed any attention to the tank sensors. After you live in a RV you will learn when to dump tanks. I also drank black tank first, then I close valve set timer for 8 minutes set time on iPhone, and repeat, Then after flushing I put in about 3 minutes, close valve. Then empty both gray tanks. Works for me. We do know boon docking at all. I had enough camping in my 26+ years of service in the US Army. We are RVer's not campers.

Happy trails.

I never drank from the black tank. There must be an easier way

 

[Hblick48]

I also have the Valterra gate valve. I put a 3" clamp around the connector end to prevent it accidentally falling off going down the road.

Hblick48,
It would depend on how your tanks are configured in your rig if this trick of sharing tank space would work.
I have a 3130re. The galley tank is mounted higher in elevation than the bathroom grey or black tanks. Therefore my galley tank will always drain into my grey or black tanks (I do the grey tank backflush trick too).
However, the 3" drain pipe between the tanks to the gate valve will hold about 8 gallons giving you some extra boondocking space for grey water. I wouldn't do it with the black tank.

All 3 of my tanks the same size and are mounted between the main frame rails on the same level.

Regarding using the "burp" method to determine when to dump the black tank, don't do it. It happened to me once (because I thought I had dumped the tank, but didnt). Burping split the seem between the top and sides of the tank. Had to replace it, and had previously replaced the main grey tank (cracked below the discharge fitting). Both are now properly supported so shouldn't have future issues.

 

[jcurtis934]

The other way around those cheap crappy sensors is to install external sensors on your tanks. The added benefit besides knowing exactly how much stuff is in those tanks, is that it takes time to pull the coroplast and install the sensors...which means less time available to maybe hoist one too many adult beverages, less time to do endless shopping for stuff you may not need, and it provides entertainment for park neighbors who wonder what the heck you are doing under there!��

 

[R.S.O'Donnell]

Admittedly not for everyone but our solution was to switch toilets altogether.

It'll be four years in March with ours. No black tank maintenance/issues whatsoever.

First learned about them from The Wynns:

 

[bcrvman]

When I flush my black tank in my 2021 Montana H/C I will dump tank first.
Then I close the valve and flush for 2 minutes, then I dump that. Then I close it off again and flush for 3 minutes and then dump again. I will repeat again for 4 minutes. Am I wasting water because my black tank sensors still do not work? The sensor shows full all the time.

I run the flush for 15 minutes when dumping on a mechanical water timer, then 15 minutes with valve closed to partially fill tanks, pull valve and put another 15 minutes on the flusher. Repeat as many times as needed to get as clean as you want. Naturally I have a 45 degree clear elbow attached to the second shut off valve to judge when clean enough. Why 2nd, so if that one fails, I can reach behind it and shut the next valve in line. With black water I want 3 valves between the crap and the outside world. I also start a 15 min timer on my watch or phone as backup to the mechanical timer. After black is done I then do a similar dump, fill, dump with the grey followed by the galley.