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Old 07-31-2011, 02:19 PM   #1
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holding tank q's

We have a wildcat 5th wheel that I either can't get the holding tanks empty, or the gauge on the wall is wrong. It has a tank for the kitchen, one for the bathroom, and one for the toilet. They all read 1/3 full, but the black one is borderline on 2/3 full. Any thoughts?

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Old 07-31-2011, 02:33 PM   #2
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The tank gauges are notorious for not working correctly and giving false readings. I rarely pay any attention to them anymore.


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Old 07-31-2011, 02:34 PM   #3
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Well, you could have crud on the sensors causing them to read this way. One way to be sure would be to use a clear elbow next time you dump. Let your tanks drain until nothing flows through the elbow. If you still read one third you probably have crudded sensors. Others suggest ice in the tanks to clean the sensors.
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Old 07-31-2011, 02:51 PM   #4
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Man I wish we had a seperate tank for the kitchen....

Can you see the tanks underneath? Ours are clear and exposed so I can see the levels..
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Old 07-31-2011, 03:02 PM   #5
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silly question but has it ever read empty at some point?
Reason I asked is if you knew that the senors were hooked up right from the start and not giving false readings.

I had an issue where one of mine was giving a false reading and I filled the tanks up and let them sit for a few to try and soften any junk on the sensor probe.

I also have a Tornado installed in my tank and use a clear elbow to make sure all the junk is out of the tank.
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Old 07-31-2011, 08:33 PM   #6
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We've only had the camper for about a month and it's an 04. The tanks are not exposed on the bottom, most of the trailer has a covering on the bottom. Where would the clear elbow be installed? When I dumped it out I went until nothing was coming out anymore and when I got home I opened them in the yard. Nothing is coming out now. What kind of sensors are these in the tank? Lastly, the black tank is the weirdest one, could it have a layer of crap in the bottom that has hardened? If I fill that tank with water, would it come up in the toilet when it's actually full? Thanks for the replies.
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Old 07-31-2011, 09:19 PM   #7
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Yes there could be some dried stuff that is causing the readings to be off. For the black tank it may be obvious what that would be, but for the gray tank you can still have "gunk" mucking up the sensors. Long soaks might help, but might not. These things are usually not accurate anyway.

The clear elbow would be installed at the camper end of the sewer hose. When you pull the valve open, you can visually observe whether the liquid is running clear or not.

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Old 07-31-2011, 09:23 PM   #8
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The following links are for reference only:

The 90* clear elbow that was mentioned looks like this - Save at RV Partscenter - RV Parts and Supply attach it to the hose and then twist it onto the dump outlet on the rig and that way you can see what's going on when you open up the tank valves.

Stock probes probably look this this (don't know for sure, i've never pulled one off) - - 226 Holding Tank Sensor Probe - Price: $2.00 - Factory RV Surplus - 1611 W Bristol St, Elkhart, IN 46514 (800) 325-1461 (574) 262-3327 upgraded probes look like this - RV Holding Tank Sensors - Get accurate grey and black holding tank monitor readings

If you filled the black tank with water, you would be able to see it come up through the toilet flap. When I end a long trip with our TT, I'll hold the black tank until either we leave or it winds up full. If it's not full when I go to dump it, I'll run water into the bowl and flush it until it is full. Then I'll dump it. Refill the black tank again with just water and then dump it again. Then I'll dump the gray tank and it's good to go. I know that this is a bit of a waste of water, but I don't have a rinse mechanism like some people do. Eventually I will, but until then, this is what I do.

Everyone will have a different way of doing things when it comes to keeping that black tank cleaned out and deodorized. My arsenal consists of using an enzyme additive called "Unique RV digest-it", calgon powdered water softener (now that I found some), and a toilet cleaner/deodorizer packet when I need to clean the bowl up. Outside of that, I guess I've been fairly lucky to not have had any problems at this point.

If you believe that your tank might have a layer of stuff stuck it, then I believe that most people on here would recommend something along the lines of filling about 1/2 of the black tank with water and add your chemical of choice and leave it all in there for a few days or so (Unique might work for this, I don't know). Then, on the day you go to dump it out, pour in a bag of ice into the toilet and flush it through and then pull the trailer around for a bit to let the ice rattle things loose to knock off anything stuck on the sensors or the bottom of the tank. Then go dump. Hopefully that will help with most of that. Good Luck!

{added} Oh I guess I should also mention that you should avoid using things like vinegar, Clorox, or anything that would "sanitize" your black tank. Enzymes and other bacteria need to survive in order for your tank to stay in good working order. If it's "too clean", then the solids won't break down as easily or at all.

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Old 07-31-2011, 09:35 PM   #9
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Horst Miracle Probe 5th Wheel Install #1

This thread is how I fixed my false indications.

I have dry camped with them 7 months now and the tanks have dumped to empty every time.

I am VERY happy with my Horst Probes.


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