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Old 09-20-2015, 04:06 PM   #1
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Black and Grey Water tanks reading empty but they're not!

So we brought our new to us camper home Labor day weekend, and parked it. Although we did not level it as we not using it just parking it to further inspect and repair. (Yay roof leaks that the previous owner said weren't there!)

When we brought it home after much checking at the previous owners home the black water read 1/3 full and the grey read 2/3 full.
Now after two weeks of being parked they both read empty?

I know they are not empty! I went in and flushed the toilet and can see stuff in there!

What gives?

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Old 09-20-2015, 04:22 PM   #2
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Now is the time to give both tanks a good flush and cleaning. You may also want to take a look at this video. Hope it helps.


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Old 09-21-2015, 05:39 PM   #3
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10 lbs of ice in each tank and drive around the neighborhood like a 16 year old.
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Old 09-21-2015, 10:27 PM   #4
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Originally Posted by tucsonrv View Post
10 lbs of ice in each tank and drive around the neighborhood like a 16 year old.
How do I get 10 lbs of ice into the grey tank?

The black tank I assume I just put down the toilet?
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Old 09-22-2015, 07:08 AM   #5
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Sorry for the error, yes the black tank you use the toilet. In my grey tank I filled it up 1/2 full and added Calgon a lot of Calgon and it helped immensely. I then started using Happy Camper in both tanks but I still on occasional throw in some Calgon. Remember when you were a kid and your mo would sprinkle some in the tub and it was so slick you couldn't stand up in it?
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Old 09-22-2015, 10:22 AM   #6
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Have never seen tank sensors fail that way but.......

My tanks usually read 1/3 to 2/3 full after dumping.. This is because of moisture/slime on the side walls of the tank It is possible the side wall dried out and the sensors now read true and the tanks are empty.. IF you have an alternate method of checking (IE Look down the throat of the toilet,, Tap on the side of the tank) that would be best.

How sensors work.

Imagine a nail driven into the tank,, IF the nail is WET, then the tank is at least full to the level of the nail.

Well, that is EXACTLY how the sensors work, only it is a metal rod and installed in such a way as to insure it does not leak.. But that is Exactly how they work.
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Old 09-23-2015, 01:02 AM   #7
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I would just double flush each of them now and then when you go camping next and you will more than likely get a correct reading
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Old 09-23-2015, 07:40 PM   #8
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I think that the ONLY time the tanks read correctly is when the sensors are first hooked up in the factory. At that time they all read empty, and that's correct (they are installed empty). After that the readings are rather unpredictable. Fill up the fresh water tank until it overflows. Then it is full. When no more water comes out it is empty. Between those two points it is a guess.

On some coaches you can see how much water there is in the fresh water tank (it is made of a translucent material). Black and grey tanks are generally made of an opaque material so you can't see.

Some people report good results with the See-Level system. Others don't.
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Old 09-24-2015, 03:59 PM   #9
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Well, this seems to be a very odd anomaly indeed! Both tanks were full, the black water tank was full FULL!
I spoke with my local RV shop, who are very nice and awash with information. After I had posted this I added a 12oz of digester per their instructions...still nothing. Then when I spoke with them today the had me shut off the water an open the toilet valve and describe what I could see.

What I could see was the nastiness and yuck one could imagine! Then they asked "how much pipe or tank can you see?"
My response "tank or pipe???"
She was full up!

So I went and dumped the tanks, looked down the toilet again, and the nastiness and yuck still existed!

I filled the bowl and flushed, and did this again and again and again and well...you get the point. None the less my tanks are now empty and while there I filled my grey water about 1/2 way up and the the gauge registered accordingly.
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Old 09-24-2015, 04:05 PM   #10
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Let me get this right. Someone sold you a motor home with full black and grey water tanks?
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Old 09-24-2015, 05:50 PM   #11
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Tuff to buy used from other people especially rvs a good inspection from roof to floor takes some time people buy to quick then find all the problems that the owner did or didn't know

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Old 09-24-2015, 06:50 PM   #12
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Try this

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Old 09-25-2015, 07:42 AM   #13
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I have used every chemical made for 20 years and started using Happy Camper and finally a no smell product that works.
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Old 09-25-2015, 06:51 PM   #14
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After our last 5er, I don't ever believe the lousy/cheap level gauges supplied by an OEM. I installed a set of SeeLevel level devices that worked perfectly. Jump ahead and we have a new 5er - and again lousy level readers compounded by a black tank that drains slowly. That tank drain problem will be 'corrected' and SeeLevels installed for next season. I also made up a flushing tool using a nylon barb fitting and a lawn irrigation sprayer head from Home Depot (the 180 degree version works best) plus a sacrificed elderly 1/2" ID water supply hose. Usually after a good flush out, the level gauges work for a couple weeks.

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