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Old 06-12-2019, 09:00 AM   #1
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Rockwood 5th wheel black water tank reading

We are dry camping for the first time. Have been out for about 2 1/2 days. Started out with an empty black tank, now itís 3/4 full and we have been extremely careful not to overdo it, if you know what I mean. Wondering if this may be a false reading or should we find somewhere to dump? Are these readings ever wrong?

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Old 06-12-2019, 09:11 AM   #2
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Readings are usually wrong 99% of the time on the black tank. The sensors get "stuff" on them and read incorrectly.

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Old 06-12-2019, 10:10 AM   #3
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Just X2 what Brendon said. The sensors are wrong more than they'e right.

If you're RV has a straight pipe from the toilet to the tank, you can take a flashlight and look down the toilet and guess at how full it is.
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Old 06-12-2019, 10:21 AM   #4
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Sensors unreliable for sure. That would be a LOT of flushing for 2 1/2 days. Prob have minimum 30 Gallon tank? Now Grey..... Maybe.
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Old 06-12-2019, 10:45 AM   #5
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The sensors are usually wrong. You will eventually get a feel for how many days it takes to fill up your tanks. Until then, remember you can tell when your black tank is nearly full when your toilet "burps" while you're flushing it. The burp is an air bubble that comes up into the toilet bowl. Don't worry it won't splatter outside of the bowl. This happens when your black tank contents cover your vent pipe connection and the flush contents force air from the tank back into the bowl instead of out the vent. Your tank is really, really full when this happens. When you see the burp, you will only have a few flushes left before completely full. Don't rely on this burp to determine when you need to empty your tanks, but you can use it as a last resort. A last resort would be if you wanted to stay out boondocking a couple more days and you haven't seen the burp, then you should be ok.
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Old 06-12-2019, 11:03 AM   #6
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As mentioned, the sensors are notoriously incorrect.

What can you do?...

If you have a straight shot from the toilet to the black tank, turn off the water pump and hold the toilet flush lever open.
With a flashlight, you should be able to see down to the liquid level, IF you have a straight shot.

On units like my current 5th wheel, there are 45ļ elbows under the toilet and you can't see into the black tank.

After many years of camping you kind of get the 'feel' for how full the tank is and how long it takes before getting full. I simply watch for the toilet to start 'burping' when flushing. When I get a little burp or bubble when opening the flush valve, I know it is getting full.

Oh... and BTW... even being careful with two of us... 5 days is the max on any black tank we've had. It's kind of a double edge sword... you need to use enough water to properly flush but not so much you waste water. We often let #1 set in the bowl for a couple visits. (with lid closed)
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Old 06-12-2019, 08:49 PM   #7
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The wife and I have went as long as 15 days on the black tank. Now the grey tanks 3-4 days max.
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Old 06-12-2019, 09:18 PM   #8
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My experience....two TT's never had trouble with sensors on either one...from 2008 to now. Last year I watched a TT with a family of four go thru their full FW tank, put in 5 full 5 gal jugs on Saturday morning. Put in 5 more Saturday evening and 3 more Sunday morning. They packed up Sunday by 10 and were gone. That was a lot of water.
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Old 06-14-2019, 02:49 PM   #9
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Thank you to everyone who replied! Your responses are very helpful!
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Old 06-14-2019, 06:28 PM   #10
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Yep, the sensors aren't worth much. Our current 5th wheel has the strangest I've seen yet. It shows empty immediately after I dump, then goes to 1/3 as it sits there empty in the yard. Same thing every time.
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Old 06-15-2019, 12:23 AM   #11
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Same on mine. We can look in & see level, so never been a problem. As far as gray water, we carry a bucket & use some to put out campfires. Helps eliminate some of it & saves potable water.

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