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Old 07-10-2011, 12:37 PM   #1
2 Rivet Member
2010 27' FB International
La Crescent , Minnesota
Join Date: Feb 2007
Posts: 96
Black water flush system

Last spring on our way back from the southeast we stopped in Jackson Center to have a few warranty items taken care of. Just as we were leaving their camp ground, we were flushing the black water system and water came out of the belly pan. Airstream returned us to service and replaced the siphon breaker on the system. We were on our way back to Minnesota shortly.

When we returned home I again tried to flush the black tank and found the flush system completely plugged. We then took our trailer to Fogdhal R V. in Waterloo Iowa. They used high pressure air to blow out the system. It now takes an hour and 20 minutes for the black water flush system to fill the black tank. They suggested that we try a cleaner which we did, with no change in the fill rate.

Fogdhal refuses to look at it again.

I suspect that when the original siphon breaker failed, a piece of plastic obstructed the line.

Any thoughts or suggestions on the cause or correction to the problem
would be appreciated.

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Old 07-10-2011, 01:39 PM   #2
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1991 34' Excella
Princeton , New Jersey
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Refusal to fix something they brake is quite common form RV dealers.

That aside I will say I have never used the Black Water Flush System and would not suggest that anyone use it. The volume of water that it sprays into the tank won't accomplish much, unless as you are trying to do fill the tank.

What I have always done while dumping is allow the tank to drain and then while the valve is still open lift the hose so as the top of the hose is above the top of the Black tank. Then open the gray water tank valve and count to 10, closing the gray water valve and dropping the hose. That flood of gray water back flushing into the black tank will do far more than a 1/2 in spray nasal ever will.

After the black tank has again drained close the valve and dump the gray tank.

Now I am sure you will hear lots of people question this method but after a career in building maintenance, lots of plumbing time, and some 40+ years of camping I think I have an above average idea of what is going on in that tank.
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1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

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Old 07-10-2011, 04:07 PM   #3
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2010 27' FB International
La Crescent , Minnesota
Join Date: Feb 2007
Posts: 96
Thanks for your idea! I will give it a try.
I would still like to get the Black Water Flush System up and running though.
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Old 07-10-2011, 04:23 PM   #4
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2005 19' Safari
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We purchased the black water tank spray system from the dealer when we bought our Airstream, but only used it two or three times. Looking down into the tank while it's spraying, all that system does is fill the tank with water. The spray is pretty much useless for breaking up solids or swirling the contents around.

Now, before dumping, we just fill our black water tank almost to the top by holding the flush pedal down. This gives a powerful flush that leaves the tank empty of all solids.

Just my opinion, but I'd save your money instead of trying to repair the spray system, unless you have leaks or something like that.
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Old 07-10-2011, 05:21 PM   #5
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2008 27' Classic FB
Burkburnett , Texas
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Siphon breaker

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I hope the photo comes along as I haven't tried this before.

Not long after I brought home our Airstream and was using the black water flush, I also had water running out the belly. This valve was secured tightly to the wall with a clamp. It was the way that it was secured that likely caused it to crack, allowing water to leak down the wall and out the bottom. I replaced it and secured the plumbing so as not to stress the valve body or its connections.

The way the valve works; water pressure forces the piston up against gravity, this applies water pressure to a spring loaded ball valve. The water pressure overcomes the spring pressure and water flows past the ball to the spray head mounted near the top of the BW tank (somewhere). The design of this valve is supposed to prevent the possibility of back flow.

On my '08 27FB, this is located under the closet accessible through the access panel. Location may vary depending on model, the location of the original leak may give you a clue as to it's approximate location. I would inspect it to see if it is still good. If the spray head in the tank is plugged this might be a difficult task.

I've never tried to fill the BW tank this way, but use it to introduce additional water before dumping and also have left it on for several minutes with the dump valve open until the drain hose ran clear. I have used it to add water to the tank before a weekend trip. Running it about 3 minutes fills the tank about 1/4 full. This is definitely not something you want to leave running with the dump valve closed for any length of time (getting distracted, etc.) or you might get a part in the sequel to Robin Williams' RV movie.

I agree that it's spray pattern may not be very effective at rinsing the tank, but it is a convenient way to add water to the tank when flushing; and I often use a couple of fill/dump cycles using it to add water to the BW tank
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