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Old 11-30-2014, 10:28 PM   #1
2 Rivet Member
Fort Worth , Texas
Join Date: Jun 2014
Posts: 34
Do You Need to Dump the Black Tank After Driving Home?

Stupid question.

Preparing to winterize for the first time. Dumped both tanks at the RV park. Flushed the black water tank pretty good and waited until it was empty before going to the grey water tank and hitting the road.

Started driving home. Took a break from driving and thought "I bet there is a tiny bit of water still in the tanks. I wonder if I pulled the lever now if I could totally empty them". I figured like an ounce or two of water might come out.

I made the mistake of pulling the black water first and dirty water started flowing out. Definitely more than just a few ounces was in there. Fortunately I stopped it right away and then went to an RV park and redumped the black waste water again. Not sure how much was in there but more than I thought.

So is there like a trap in the black water and this waste in the trap got dislodged from driving and this what was coming out? Should we always dump after driving home and things get sloshed around? I can't totally figure out why if I felt the tank was empty at the RV park originally after driving there was some waste in there.

I'm not sure what exactly was going on.
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Old 11-30-2014, 10:36 PM   #2
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1999 34' Excella
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Hillsboro , Texas
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Howdy! There is a possibility that a 'solid' or TP may have dammed up some water by the Black drain. Driving dislodged. I have always 'fresh water flushed' our Black tank before towing.

Another possibility is that the AS may not have been 'level' and liquid was on the opposite side of the BW tank drain. Just guessing, of course.

Now, I know about how much water to put into the BW tank as a 'rinse' after dumping. If I get more 'solids' or TP, I may go for a third... Your profile doesn't display the AS you have, so, I don't know if you have a BW tank 'flush' feature. If you do, use it.

I also use the same 'BW Flush' to add water to the BW tank prior to trip home. I can then get more 'sloshing' around on the trip.... and if storing over a week, I drain into my home dump (cleanout on home plumbing).

Hope this helps..
Peace and Blessings..
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Old 12-01-2014, 06:43 AM   #3
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2012 Interstate Coach
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My Airstream Interstate has a wet bath, so the shower hose reaches the toilet. I also have an exterior shower within easy reach of the black tank flush fitting. Both of these give me the option of adding HOT water to the black tank.

Since my gray tank always fills faster than my black tank, and when I dump my tanks I always dump both tanks, I take the opportunity to top off the black tank with HOT water shortly before dumping. This helps to soften any solids and ensures that when I dump the black tank, I get a more complete dump.

If you don't have a shower hose that will reach your toilet, and don't have an exterior shower with hot water, and don't have a black tank flush fitting, you can still do the same, by filling a bucket with hot water and dumping it in the toilet.
I thought getting old would take longer!
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Old 12-01-2014, 06:49 AM   #4
1987 Avion 34W owner
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Good Ol' , USA
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We dump our black tank before we leave wherever we have been parked. Then I add several gallons of water to the black tank so it can slosh around as we're going down the road. Then, I like to flush it again with lots of water once we get home. Our sewer cleanout on the house is close to where we park the trailer, so it's pretty handy.
I this great country!!!!
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Old 12-01-2014, 07:15 AM   #5
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1991 34' Excella
Princeton , New Jersey
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Unless they are almost brand new neither tank will ever completely drain. Without going into details just accept that fact. The amount of water that remains in the tanks will not hurt anything. Even if freezing does take place the ice has no place where it can be confined and thus do any damage.

If you are winterizing there will be water in the traps that will be moved to the tanks when you put antifreeze in the traps. If you are still concerned pure 8 or 10 oz. of additional antifreeze in the black tank via the toilet.
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Old 12-01-2014, 07:17 AM   #6
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1965 26' Overlander
Ferndale , Washington
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I always 3x flush .... one way to help clean the tank is to pour a couple bags of ice cubes into the toilet before you hit the road and that will help mechanically scrub the tank.
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Old 12-01-2014, 07:28 AM   #7
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1987 25' Sovereign
Oregon , Ohio
Join Date: Aug 2010
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This past summer we stayed in two different campgrounds that the dump location sloped away from dump opening. I had to use my trailer leveling blocks to get the trailer to level for a complete dump. I am amazed at the way some places are designed. It is like the engineer has never camped or even researched what was needed.
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Old 12-01-2014, 10:27 AM   #8
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1978 28' Ambassador
Pacifica , California
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Ice cubes in the black tank? So smart! And hot water trick too! I love the practical solutions you guys have here.
Keep on truckin!
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Old 12-01-2014, 10:29 AM   #9
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Originally Posted by laducky View Post
Ice cubes in the black tank? So smart! And hot water trick too! I love the practical solutions you guys have here.
Go easy on the praise lest I get a swelled head! Especially since my head is already larger than my hair!
I thought getting old would take longer!
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Old 12-01-2014, 11:25 AM   #10
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Don't feel bad Protag, it's a sign of brain energy!!!!

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Old 12-01-2014, 01:43 PM   #11
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2014 22' FB Sport
San Antonio , Texas
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I tried a new (at least to me) dump method this past trip. When ready to dump the black tank, if it is not full, I just depressed the toilet foot pedal and let the water run and fill the tank. I relied on my eyes and a flashlight while looking down "the hole" to determine when it was filled. Then a full tank dump, followed by refilling the tank, again while holding down the foot pedal. Full tank dump #2. Tank appeared to be spic and span.

I have the black tank flusher, but it needs a warranty claim because it has a slight drip from under the trailer while in use. However, the method I described above actually seems easier because I do not have to mess with hooking up a junk hose to the flushing port and a water supply, nor do I have to run back and forth checking on the status of the level.

I finished by again flushing the toilet for a 20 second count which I estimate will introduce about 2 gallons into the tank, followed by my tank treatment liquid. Done.

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Old 12-01-2014, 02:56 PM   #12
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On our last trip home for the year we will do a dump at the park we are leaving - then put in fresh water to roughly fill the tank up to about a 1/4 full and then add a 1/2 cup or so of water softener. Once home we do our final dump at our local park - for this one we will raise the curb side of the trailer with a 2X8 - do the dump - and then a final rinse just filling the toilet and flushing it several times. The sloshing around on the trip home with the water softener seems to dislodge any solids that have found a home against the tank walls - at least that's the theory - seems to work.

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