Cleaning Berk Black Tank Sensors with a Cross-Feed Backflush

[gordonsick]

In an earller thread (http://www.forestriverforums.com/for...rs-142340.html), I noted a problem of cleaning the black tank sensors on my Berk that arises because the tank flush sprays into the passenger side of the tank. It cannot spray onto the sensors, which are on the driver side, behind a "slide" that diverts effluent from the toilet away from the sensors.

This problem is specific to the design of a Berk, although it may occur on other RVs, as well.

But, I realized that the Berk has another design feature that can provide a solution.

The solution arises because the Berk has a large 4" waste pipe coming from the grey water tank, while most RVs have a 2" grey water waste pipe. Moreover, the grey and black waste pipes join after their flush valves, but before any significant drop. Using a clear fitting just below the waste pipe, I’ve noticed that the grey water tank fills up the flush hose and develops an internal back pressure. This pressure will be increased with any constriction on the flush hose, such as by raising the flush hose.

The procedure is simple:
1. Dump the black tank and flush as best as possible with the tank flush hose.
2. Close the black tank valve, and flush the grey tank.
3. As soon as the flow from the grey tank backs up enough to fill the hose, open the black tank flush valve. This allows the grey water to enter the black tank with some force, right at the point where the black sensors are mounted.
4. After a suitable time (experimentation helps), close the grey water tank valve to allow the black tank valve to flush.
5. If you see new residue, you are successful. If not, try it again the next time you dump waste.

I’ve tried a variety of other techniques, including the GEO method, but they didn’t result in immediate success. This method gave me success after 2 or 3 tries, so I can recommend it. It doesn’t necessarily replace the other techniques, but it is worth trying.

–Gordon

[GoneSouth10]

Gordon - Not sure if your issue is actually cleaning the black tank sensors so they work or just getting every last bit of the last "stuff" out of the tank, but for cleaning the sensors (i.e., when your LED reading in the control panel shows a full black tank even though you've just dumped it), I've found this stuff works like a champ!
https://www.amazon.com/Caravan-Overn...ack+tank+flush

I had not only the mucked up sensors that were giving me the false "full" reading, I also had a NASTY tank order (Full disclosure - the OE indicator was flashing on that one - pure Operator Error. Put the coach in storage after a long trip thinking, "Oh, I'll swing by this weekend and go dump the black tank." Three months later - NASTY. Never make that mistake again!!). At any rate, this product cleaned all the sensors and eliminated a very nasty order problem basically overnight.

[gordonsick]

GoneSouth,
One of my problems is scale on the sensors from hard water. When I see scale go through, the problem tends to clear, but only for a while.

I'm not sure if the sensors extend into the tank or are flush inside the tank. If the former, then toilet paper and waste matter can be a problem.

I've used commercial sensor cleaners like the one you recommend, plus the GEO method, which can reduce scale, if used every time. The problem with the chemical methods is that they work once, and then the sensor starts to misread. If I have to use the chemicals every tank cycle, they become very expensive. The GEO method is less expensive.

So, the advantage of my crossfeed backflush method is that it is free and I can use it every cycle.

--Gordon

[GoneSouth10]

The Caravan product is actually a microbial-based solution, so I've never had any problems with the sensors afterwards (and I've probably gone through 5 or 6 cycles since I "fixed" the sensors/order problem). Not sure if it would address the scaling problem.
For my own edification, what is the "GEO method"?

[gordonsick]

The GEO method is to mix Calgon water softener (available in US from Walmart) with bleach and detergent.

In Canada, Calgon is unavailable, for some reason, so I use Borax to soften the water.
Gordon

[fckohn]

can you provide the recipe for quantities of each product fro the GEO method?

[gordonsick]

Charles Brini discusses his GEO method in detail at https://sites.google.com/site/cbruni/

Gordon

[dnicoll]

Originally Posted by gordonsick

The GEO method is to mix Calgon water softener (available in US from Walmart) with bleach and detergent.

In Canada, Calgon is unavailable, for some reason, so I use Borax to soften the water.
Gordon

Thanks Gordon! I know about GEO method but I have never been able to find Calgon in Edmonton! So you just replace the quantity of calgon with an equal amount of Borax?

[gordonsick]

Dave,
It never hurts to use too much, so use at least as much Borax as Calgon.

Part of the issue depends on how hard the water is. If the water is hard, like in Alberta, you would need more Borax or Calgon.

Walmart in Canada does sell Borax and or Boraxo. Different brands but same stuff.

There is a lot of discussion of Borax vs Calgon in threads about washing baby diapers. In that case, Calgon is preferred because it is (mainly) a non-precipitating water softener. I guess it binds the hard minerals in the water and keeps them in solution so that they are rinsed away. But, a precipitating water softener apparently converts the hard minerals to something that precipitates out of water and falls to the bottom. Fortunately, our black water tanks are tougher than a baby's bum, so Borax should be OK for us.

–Gordon

[gordonsick]

I started this thread to explain how I cross-feed grey water into the black tank to help clean it out. I originally thought that this needs the full-size 3" drain pipes on a Berk to work properly.

I have now revised the technique so that it should work on any RV that uses same drain hose connection for the grey and black tanks. And, it now works better on my Berk.

The change is simple. Just modify my original procedure by leaving the black tank valve open while you lift the drain hose, before opening the grey tank. This allows you to get more grey water into the black tank, and it works even if you only have a 2" drain pipe on the grey tank.

The new procedure is:
1. Dump the black tank and flush as best as possible with the tank flush spray.
2. Lift the drain hose so that it is above the level of the drain pipes from the grey and black tanks. This is easy if you leave the black tank valve open, so that any remaining water in the hose easily drains away, making the hose light.
3. Open the grey tank valve. Since you are holding the hose high, this causes the grey water to cross over to fill the bottom of the black tank. Do this for a brief time, so that you fill the drain system of the black tank, but not so long that you force black tank debris higher into the tank.
4. Close the grey tank valve and lower the hose, allowing the cross-feed water to drain from the black tank.
5. Repeat the process, starting from step 2, but allow more grey water into the black tank. This way, you are removing excess debris from the black tank, starting at the bottom and working up.
5. Repeat until you run out of grey water or see no residue coming through. It helps if you have one of the clear pipes connecting the tank valve to the drain hose, so that you can see your progress.

–Gordon