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Old 11-01-2014, 09:26 PM   #1
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Reverse flush the black water tank?

I am a newby and was thinking the other day(I've gotten in trouble doing this in the past) about a way to reverse flush the back water tank. This is probably ludicrous but I'll ask any way. Would it be possible to do the following: 1. drain the black tank in the standard fashion
2. put the outside cap back on the common drain(that drains both the gray and back water tanks)
3. open the full gray water tank valve and let this high pressure
water run backwards through the connecting pipe, into the back water pipe and into the black water tank.
4. Then before the pressure equalizes in the two tanks quickly shut off the gray water drain valve so no black tank water gets into gray tank. 5. Then once again drain the black water tank in the standard fashion.

I can hear the old timers now. "what an idiot!" But none the less, is this doable? Thanks
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Old 11-01-2014, 09:34 PM   #2
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Sure,let us know how it turns out! Just use whats left of the Gray for final rinse! Youroo!!
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Old 11-01-2014, 09:35 PM   #3
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I agree, stop thinking! I have the same problem, I'm an idea man.



It would back flow into black tank until the pressure equilized but WHY would you want to do that?

It would not effectively clean your black tank, potential put black tank materials into grey tank and you would loose having the soapy gray tank water to help flush out slinky.


There are much better ways to clean the blank tank
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Old 11-01-2014, 09:43 PM   #4
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Hey Indymule, are you going to (The Big Show) Westminster? Youroo!!
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Old 11-01-2014, 09:53 PM   #5
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QUICK HIJACK

No after Amana, I can't lower myself to do Westminster

NOW BACK TO YOUR REGULARLY SCHEDULED THREAD
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Old 11-01-2014, 09:59 PM   #6
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Oh and by the way Lon,

There would still be gray/black water in the pipe (not a lot but enough) when you removed the cap again, thereby giving you another shower.

Just a thought!
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Old 11-03-2014, 12:15 AM   #7
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Thanks. What stimulated these erroneous thoughts was the realization that when its time to shut down and get back on the road my gray tank is full and the black tank is only a quarter full. So I mused there ought to be a way to get that perfectly good soapy water from the gray tank into the black tank for a good purge. It could be pumped over with a backflow preventer. Forrest River could offer this as a thousand dollar option and I won't charge them a thing. :-)
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Old 11-03-2014, 05:50 AM   #8
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Quote:
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Thanks. What stimulated these erroneous thoughts was the realization that when its time to shut down and get back on the road my gray tank is full and the black tank is only a quarter full. So I mused there ought to be a way to get that perfectly good soapy water from the gray tank into the black tank for a good purge. It could be pumped over with a backflow preventer. Forrest River could offer this as a thousand dollar option and I won't charge them a thing. :-)
I don't know if you could have enough pressure to do what you want. Your discharge lines go's down on both so you would have to go up hill while still holding the black in the tank which is above the outlet. Wouldn't it be easier to just dump your gray in a bucket and dump it in the toilet?
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Old 11-03-2014, 07:33 AM   #9
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First things first, you need a valve on the outlet, not a cap. Twist-on Valve - Valterra T58 - Sewer Fittings & Adapters - Camping World Unless you want to be like Robin Williams in the movie RV!
Water will run up hill because water seeks its own level. If the water level in the grey tank is higher than the water level in the black tank (and it would be if the black was empty and the grey was full), the water from the grey tank will enter the black tank until the levels are equal. You would then want to close the grey valve and open the twist on valve to empty the black tank again. Finally, finish up by closing the black valve and opening the grey valve. I've done this when I couldn't use my tank flusher, but it surely does not work as well as the flusher.
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Old 11-03-2014, 08:00 AM   #10
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Why not keep it simple (and prevent the "Robin Williams moment") by draining your black tank and then refilling it with fresh water via the commode and dumping it again?
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Old 11-03-2014, 08:30 AM   #11
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Quote:
Originally Posted by Lon View Post
I am a newby and was thinking the other day(I've gotten in trouble doing this in the past) about a way to reverse flush the back water tank. This is probably ludicrous but I'll ask any way. Would it be possible to do the following: 1. drain the black tank in the standard fashion
2. put the outside cap back on the common drain(that drains both the gray and back water tanks)
3. open the full gray water tank valve and let this high pressure
water run backwards through the connecting pipe, into the back water pipe and into the black water tank.
4. Then before the pressure equalizes in the two tanks quickly shut off the gray water drain valve so no black tank water gets into gray tank. 5. Then once again drain the black water tank in the standard fashion.

I can hear the old timers now. "what an idiot!" But none the less, is this doable? Thanks

What about the gallon or two of liquid between the black/grey valves and the cap to the sewer outlet. Could be a nasty surprise when you remove the cap to attach the drain hose.



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Old 11-03-2014, 08:53 AM   #12
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Watch all of this ...

http://www.forestriverforums.com/for...son-70514.html
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Old 11-03-2014, 09:23 AM   #13
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RV Hydro Flush 45 Degree - Valterra F02-4100 - Sewer Flushing - Camping World

I use one of these with a dedicated hose.
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Old 11-03-2014, 09:36 AM   #14
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Isn't one of reasons we have 2 separate tanks to minimize the chance of cross contamination?

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Old 11-03-2014, 09:46 AM   #15
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I'm not a fan of the idea because you'd be introducing black water into the grey water tank. But that said to get it to work you'd need to add a second gate valve to keep the mixed dirty water away from the cap or you'll get a nice shower when you remove the cap to reconnect the sewer hose.

There was another thread here recently about taking the sewer hose once it's full and lifting it thus forcing a wave of dirty water back into the tank in an attempt to clean out a little more. If you have 3 hands you might be able to do some fancy gate action to get the grey into the black using this method. Wear & tear on the sewer hose and increased potential for a disgusting catastrophe are the obvious deterrents.
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Old 11-03-2014, 10:34 AM   #16
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First as others have mentioned you would be wearing it when you took the cap off, second this wouldn't stir things up enough to do much good. I don't think those back wash pieces you put on and connect the hose to work enough. I like the wand, with the flexible hose, that goes in through the toilet. Just wish you could see to control the end so you get everything. Use it a couple of times a season so you don't get any build up. If they made the tanks so there were no corners at the discharge end would help.
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Old 11-03-2014, 10:37 AM   #17
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in order to avoid any cross contamination and the possibility of a grey or black water bath, i would use this

Amazon.com: Valterra F02-4350 Reverse RV Flush Valve: Automotive


I used it last week to flush my black tanks b4 I put it away for the winter.
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Old 11-03-2014, 11:30 AM   #18
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I threw away ALL my "hose/clear plastic" type flushers and installed a turboflush in my gray tank as well as the OEM one in the black tank after watching that video.

Those "back flush" types are a waste of money IMO. I also have an end cap shutoff valve but only use it to prevent "wet shoes" in case a valve sticks open.
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