# Grey and Black Water Holding Tanks



## RCCL Cruisers (Apr 17, 2004)

Seem to be having a problem getting my tanks empty, I open the black first until it runs dry then drain the grey tank but once everything has been drained they both still showing a 1/3 full on the panel but are bone dry. Have not put any toliet paper down have been using the proper chemical but no luck. I am thinking I may have a faulty sensors on my hand for the panel on the wall. As anybody else had this problem, I was thinking about putting my presssure washer to the pipes to see if something has go jammed up before the dealer has my trailer.

RCCL Cruisers


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## Y-Guy (Jan 30, 2004)

RCCL I would high recommend one of three options. 1) Get a Quickie Flush, and install it or have it installed, it sprays down the sides of the tank, 2) Get a Flush King, which allows you to back flush a tank to clear it, down side is it can take several fills to clear the tank, 3) Get an extra hose and buy a flush wand (wal-mart/camping world) to do a manual flush of the sides.

You'll find several threads as Thor noted, about these topics, including how totally unreliable the panels are even when they are 100% clean. A quick search will probably give you more than you ever wanted to read about the monitor panels. My black tank almost always reads 1/3 full even with a couple of gallons in it. The best way to judge is to open the toilet and look down.


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## hatcityhosehauler (Feb 13, 2004)

Like Y-Guy said, the gauges are notoriously inaccurate. This is not specific to Outback's, as most stock RV tank gauges are of the same quality. there are a few after market gauge systems out there that are mentioned in some of the other threads. I don't know if they work any better or not.

Tim


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## hurricaneplumber (Apr 12, 2004)

Previous Thoughts to consider about inaccuracies and tank volumes capacities

One huge thing to think about is how the tanks are constructed. The holding tanks are about 7" high and about 84" wide. With level sensors at Empty, 1/3, 2/3, and Full, that means that each sensor probe is in close proximity in the vertical height. By having such a wide tank and shallow height, any movement in the water can cause inaccurate reading by sloshing to the next sensor. Since they use a conductivity sensor which measures current by being wet, when water sloshes around and hits another sensor it will register that sensor, it takes time for the adhesive effects of water to move off of the sensor, hence it will register a different level until it settles down and dries out. Since the grey tank is used the most, I would assume it has the most movement within the tank. I bet if it could sit unused for a day or so it would read more accurate as the water finds its level and any other sensor dries off. And think about the black tank, there is other "stuff" besides water that can touch a sensor and cause a inaccurate reading.

This is why they sell the blue tanks. I use my 10 galloner to take out enough grey water to get me through the rest of the weekend.
I used to panic thinking I was in trouble, sitting there watching the levels, now I just pop out the blue tank and in 10 minutes there are no more worries, just more time to sit back, crack a cold one, tell some jokes and enjoy camping.

Just some more thoughts.

Good Luck

Kevin


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## Ymryl (Mar 2, 2004)

You could always try "The Geo Method". Basically, he suggest using Calgon water softener in your holding tanks. Quite a bit of discussion available about his ideas, check out the various threads.


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## BigBadBrain (Aug 26, 2004)

Hurricaneplumber

My math may be off but if your camper is out of level by 1 degree, it could represent an error of one and a half to two inches over 84 inch width of the tank. That represents over a quarter of tank inaccuracy IF the sensor is mounted at the end of the tank. If the sensor was mounted in the middle of the tank, errors in leveling could be reduced to almost nil (the center being the average level of the fluids). If the camper is still on its springs, where you stand and how you hold yourself could also have some impact (especially for heavy loads like myself). Do you know where the sensors are located?

I wonder what the average level can produce for leveling a camper in terms of degrees? I'd guess one or two degrees max. Certainly would have trouble with accuracy if you were simply pulling into a rest stop and wondering if you should empty the tanks (or fill fresh).

Also, if one were to put in new sensors, the middle of the tank's long side would be best and the end of the tank would be the worst.

I guess this is kind of obvious but I really hadn't thought how thin the tanks are until you pointed it out.

Brian


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## jallen58 (Oct 27, 2003)

2 Degrees across 8 feet is about 3-1/2" so i would say most leveling of a tt is close to 1/2 a degree. My level system alwys gets me within 1/2 degree or closer

Brian i replyed to your e-mail question.

Jim


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## hurricaneplumber (Apr 12, 2004)

Brian,

I believe the sensors are located at the drivers side end of tank, roughly centerline front to back. I have a picture of them if I can find to show you. I know that is the way the fresh water tank is layed out, I will check again though.

Excellent idea about the level thing. Last time I tried something new for dumping.
I emptied the black tank and then lowered the tongue jack a few cranks so the black tank outlet was lower towards the drain valve, amazing the extra amount that came out. I then raised the tongue jack as high as it would go, opened the black valve and then opened the grey valve, which empties the grey into the black tank at a pretty good velocity, then closed grey valve and lowered tongue again to drain black tank again. Lots of cranking, power tongue jack would be nice. All of this managed to easily empty both tanks and clean the black pretty well.

I still think most of the errors are caused by tank and sensor design/placement. 
Maybe I will try to insert a flexible light and mirror system to catch a glimpse of what the tank inside looks like, the sensors barely protrude into the tank.

This can all be analized anyway you want to I guess, I just look down the toilet and wait for the shower to back up before worrying about tank levels. And with the 6 volt batteries I don't even bother checking the wall monitor, I know I can go for a long time as long as you conserve.

Kevin


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## begood (Jun 9, 2004)

is your black tank located back of the trailer and the gray one fornt of the trailer? on my trailer (26rs) the black tank is front and the grey one is back. In my case i would need to raise the trailer to empty the black tank. am i wrong on this?


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## hurricaneplumber (Apr 12, 2004)

2004 28BHS:

Black tank located in rear, drain outlet is towards front of camper in center of tank.

Grey tank located ahead of black tank towards front, drain outlet is towards rear of camper in center of tank.

Fresh water tank is located under bed in front of camper, drain is on drivers side as well as fill piping, tank bottom has a recessed divet with drain cock located at bottom of it.

KS


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## BigBadBrain (Aug 26, 2004)

In an earlier post, the idea of putting on the exterior (non-penetrating) type sensor for monitoring tank levels was put forth. I had a fifth wheel with this kind of sensor setup and it seemed to work most of the time. (I think, however, that the tanks were deeper than the 7" tanks on the Outback). I wonder if these types of sensors would be less prone to debris on the inside of the tank causing erroneous readings.

Has anyone tried these types of sensors on the flatter tanks?

Brian


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