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Old 06-03-2013, 02:25 PM   #1
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Black water tank won't completely empty

Hello all,

A little background...I have a 2012 Forest River Grey Wolf that I bought new in January 2013 and have taken it out three times and noticed that after emptying both the gray and black water tanks the black tank never shows comepletely empty.

After my last trip I used the dump facility at the campsite I was at and noticed that the black wanter tank emptied quicker than I thought it should have for 4 days of use, but drove home and decided to check it again and sure enough there was still liquid in the tank. The more I looked at the tank and the drain valve I noticed the bottom of the tank was lower than the drain valve...which I found very odd!

Question: Why would any RV manufacturer design a holding tank where the bottom of the tank is lower than the drain valve resulting in always leaving liquid in the tanks?

I suppose I need to raise one side of the trailer while I'm emptying it, but again I'm puzzled at the desing of the tank/drain.

Any thoughts on the topic would be appreciated!


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Old 06-03-2013, 03:15 PM   #2
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Welcome to the forum.
Can you post a pic of the issue so we can see what you see? I am sure we can help you figure it out.

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Old 06-03-2013, 05:37 PM   #3
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Black water tank won't completely empty

Hi Crunchman,

Here's a crude drawing of what I'm talking about, since I'm at work and my rig is at home. I hope to be able to get some decent pictures tonight, but the attachment should show what I'm dealing with.

Now, if I remember correctly from my last trip and looking at the black water tank it appears to sag a little bit at the bottom, which might be why everything isn't draining from the tank. I wonder if this might be a warranty repair issue?

Thanks for taking the time to help!
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Old 06-03-2013, 06:26 PM   #4
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Mine was the same way. I would drain the blk tank, refill it w/water drain it again that would usually get all the solids out. Some water left in is ok but if it shows 1/3 then your idea of tilting a bit is easy. Drive the TT onto som 2x10 planks to get the extra help to drain. Easy and fast.
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Old 06-03-2013, 06:59 PM   #5
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It could very well be showing 1/3 full because the tank sensors are dirty or fouled.

Tethford makes a sensor cleaner that works pretty well, BUT you have to do a heavy application AND agitate (drive around with it in the tank).

Other than that, the GEO method several times with mucho flushes.

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Old 06-03-2013, 07:47 PM   #6
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Is the tank itself, black? It should be.
A black tank should look like these;
RV Waste Holding Tanks for Sale - PPL Motor Homes
See if you can get a new tank installed.
That aint right.
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Old 06-03-2013, 08:42 PM   #7
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UPDATE - Black water tank won't completely empty

Wow, one reason I love this forum is that there's always some GREAT ideas and usually a solution!!

Here's the most recent update... I took a look at the tank tonight when I got home and discovered that the tank indeed does sag/angle towards the drain valve which is fine, but a couple of inches before the valve it rises again keeping unwanted liquids inside of the tank. Sure sounds like a warranty issue to me I took about another 3 gallons of "grossness" out of it tonight since where it's parked there is a slight angle towards the drain valve, but should I really have to do that on a slant? I think not!

Twisty, thanks for the diagrams! It makes perfect sense that the tank should slant towards the drain vavle!! I guess I need to call the dealer and see what they say!

BigTJohn, what an incredibly awesome and easy idea about the 2x10 until I can talk to the dealer about having the tank replaced!! It might look a little strange pulling up to the dump station and driving onto a board, but if the results work.... who cares!

Thanks to everyone for the input!

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