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Old 04-22-2009, 08:25 PM   #1
Join Date: Nov 2008
Location: MD
Posts: 80
Aaaaand another newb question...

Black tank (and sure, gray too while we're at it).

We took the 1st (and only) trip in the Roo (2007, 17') a couple weeks ago, and after a day or so saw the black tank was 3/4 full, and the gray full. So DH goes out and empties black, then empties gray. Well the black tank reading never came down, gray then said 1/3 i think.

After another day, black reads full, gray is up there. He does the same thing again and STILL black is not going below 3/4 full.

We ran A LOT of water down the toilet and again into the gray tank even tho we were getting ready to go. Had chemicals in the toilet too. He even went out and rocked the camper a little. (friend suggested maybe something was blocking a sensor?) Emptied and still reading 3/4 full.

Are we doing something wrong? Anything else we can troubleshoot? We are going out again this weekend. TIA!

CDR, U.S. Navy
Me, him, 2 kids, 1 dog
F-350 (V-10) to tow
2010 Rockwood Signature Ultralite 8317RKSS
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Old 04-22-2009, 08:46 PM   #2
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Join Date: Sep 2006
Location: Southern Ontario
Posts: 774
Sensors are problematic at the best of times. I see your trailer is an 07. Doubt they are reading correctly.To see for sure when looking down toilet bowl with trap open hold flashlite plug nose and you should see bottom of tank or get an idea how full it is. They are really not deep perhaps 6-8" on your trailer. Hopefully you do not see a mound of you know what. Gray water when drained should be empty. Not much to plug that tank. I think it would take a good week of using toilet to fill black tank depending on use. We use toilet for solid waste only if we have to. Rather use campground facilities if possible. Saves plugging and filling black tank.
Don't worry as you will be seasoned pros before long. There is a learning curve and we even forget things over the winter.

2008 Cardinal 30RKLE 5th wheel sold
2006 Rockwood 2607, 2001 Traillite
55 nights 2009, 53 for 2010
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Old 04-22-2009, 09:20 PM   #3
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Join Date: Aug 2006
Location: Prairieville, Louisiana
Posts: 1,927
Cleaning RV Holding Tanks and Sensors

Before driving to a destination at least 20 miles away, drain both the gray and black water holding tanks. Then fill both tanks about one third full with clean water. Add about 1/3rd to 1/2 cup of Blue Dawn Dishwashing Detergent to each tank. Add the detergent to the black tank via the toilet and to the gray tank through the kitchen sink. Flush enough water after adding the detergent so that all the detergent goes into the tank.....probably about a gallon. Then drive to your destination. When you reach your destination, drain both tanks. This procedure will help clean the tank sensors and lubricate the dump valves.

Note: You may have to repeat this procedure several times to really get the sensors clean.
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Old 04-22-2009, 09:26 PM   #4
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Join Date: Sep 2008
Location: Colorado
Posts: 454
Originally Posted by dezolen View Post
...are really not deep perhaps 6-8" on your trailer...

I thought my tank was frozen.

I've been looking in mine all winter and I don't even see the antifreeze i flushed through the pipes last fall and was thinking that maybe there was water or something and it froze and that's why the "bottom" looked so shallow.

I read in another thread about how to use calgon to keep the water soft and it actually helps keep the sensors clean maybe i'll have to run some of that through this summer and see if my sensors start reading correctly too. Last time i checked them, they were reading 3/4 on both tanks also. (after some research, it might have been here that i read about the calgon thing -

Interesting stuff!

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2000 Rockwood Roo M-18 Hybrid
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Old 04-23-2009, 05:40 PM   #5
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Join Date: Jan 2007
Location: Camano Island, Washington
Posts: 10,193
sensors are famous for not being accurate.
probably TP on the sensors.
there are numerous things you can do but the bottom line is never rely on them being accurate.

you can invest in tank sprayers, like the Tornado. or back flush devices, like Flush King. or get a tank wand to stick down the toilet hole and spray the sides/sensors.
we also dump our ice in the black tank, on the way home. it helps scrub the sides of the tank while in transit. of course that's with some water in the tank.
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