Need help regarding black tank flush

[rlhendren]

So my new-to-me 2011 23D was previously always hooked up at a campground with sewer, so the owner said he never even used the black tank. He just left the valve open. I'm assuming he also never used the black tank flush, though I don't know that for sure. This weekend, I hooked up the sewer line, drained the black tank, then hooked water up to the black tank flush valve. No more water came out of the sewer hose, but lots of water came out from under the trailer. It seemed to just be running from all around the aluminum tank enclosures. Does this mean that my black tank flush is not actually hooked into the black tank and instead the water is just running down the outside of the black tank? I'm assuming that since the black tank is below the trailer, that I don't need to worry about water damage, because all of that water essentially went on the outside of the trailer (even though it was inside of the aluminum under belly enclosure. Can someone tell me if I'm correct?

Thanks

[AWCHIEF]

If the PO never actually used the black tank and just let waste run straight thru. I would not be surprised if there was a large build up of solids in the tank.

[SeaLevel]

Just leaving the black tank valve open is very bad. Even when hooked up to sewer you need lots of water in the black tank and you need to drain it all at once. It also sounds like you may have a leak in the black tank flush water lines, which could be leaking inside the trailer walls.

Figure out the possible leak first, and then clean out the black tank. You may need to fill it with lots of water and tank cleaner and drive around to break down any piles that have built up.

[mojo]

Get some RV Digest It and follow directions for soak and flush of tank. Your black flush line could have a break in it...either at the top of the tank or the back flow preventer inside the wall of the trailer.

[CDONA]

The black tank flush system doesn't have a city water pressure reducer inline like the city fresh in. These have a tendency to blow out and cause water to go elsewhere, threads on this if you can get "search" to find them for you.
When I use mine, I ease the water flow on, so no big shock as the air bubble turns to water on start up.
Yes, the PO didn't do you any favors on leaving drains open. I always add at least a bowl full of water to the black after draining.

[sburrw]

Same thing happened to me. I found this from 2010, but haven't tried it yet:

"This happened once to me with our 23' Safari. It turned out that I didn't have the water all the way on. The valve won't close until there is a certain pressure in the water line. After I shut off the water and turned it on again full, the leak stopped. Never have had trouble with it again.

At a visit to JC after this incident, the service center confirmed that this was what happened and how it works.

[GeeSag]

You might need to check your Back-flow preventer / Check valve....I had mine back-flow preventer / check-valve pop the top off and leaked water like mad. It was easily replaced. Now I use a pressure regulator when I hook up the black water flush. The back-flow preventer/check-valve was made of plastic.

[The Ice Man]

What GeeSag said.

The Backflow preventer installed at the factory is plastic and tends to fail - mine did - and the dealer will replace it with a brass fitting (at least mine did - Desert Autoplex in Phoenix, AZ).

Also heed the advice of numerous others. Never leave black valve open. You likely have a mess on your hands and will have to literally chip away the pile of solid - really solid - waste beneath your toilet. One option is to fill the black tank 2/3rds, 3/4rs full and put an ample supple of strong drain cleaner and drive the load around. If you're lucky it will soften the pile of waste. May take as many as a half-dozen trys/attempts. If not chipping is the only way I know of.

[KJRitchie]

The backflow preventer is a cheap clear plastic device that breaks easily if not flush out with air over winter storage. Same thing happened to my preowned Classic 25fb the first time I used the black flush. I replaced the valve with an elbow fitting.

Kelvin

[TomKirk]

If black tank has always been open, and if blank tank has never been flushed, I'd say you've got a bona-fide clog.

For starters, peek thru the toilet valve and see if the tank is full. If it is, there's no way to back-flush it. You'll hafta call a septic tank pumping service. They can suck it out. YUCK!!

Tom

[rlhendren]

Thanks for all the help. Probably a cracked back-flow preventer. I'll simply remove it and replace with an elbow.

As for black tank valve being left open all the time, I'm still not entirely certain that the tank is full of solid waste. When I look down through the toilet, I see the shiny floor of the bottom of the tank. But I'll still fill it half full and get something to add to break up any solids that I can't see. Thanks for the advice.

Ryan

[GeeSag]

You might also onsider using a couple 20 lb bags of ice.
Pour them in the Black tank when fairly empty and find a curvy road to drive several miles.
Let the ice slosh around to ehlp dislodge any solids buildup.

[Adventure.AS]

Originally Posted by GeeSag

You might also onsider using a couple 20 lb bags of ice.
Pour them in the Black tank when fairly empty and find a curvy road to drive several miles.
Let the ice slosh around to ehlp dislodge any solids buildup.

James from the FitRV.com has totally debunked the idea of using ice cubes to clean out a black tank. Check out his video.
https://youtu.be/iH6acEmqvcw

[dkottum]

Maybe he's telling the truth, never dropped any solids into the black tank. Push down on the flush lever with your foot and look straight down with a flashlight. See if there's a plastic bottom or a pile of you-know-what.

The external flush hookup assembly has a plastic check valve on the inside which may be broken from freeze-up, spilling water inside the walls. You should be able to see through open cabinetry the condition of the valve with a flashlight.

[rlhendren]

Thanks Doug. Looks shiny using a flashlight. I'll check the valve inside the cabinetry next.

Ryan

[RadioGuy]

Any Leak in the black tank is a problem. In some places, even in your own yard, your neighbors can turn you in if you're filling and rinsing and most of it is going right into the yard from the leak(s). Black tanks are supposed to be emptied into a qualified sewer or septic system but NEVER on the ground. Driving around with a leak can also get you into big trouble...I never like the idea of driving around in order to "Stir" the tank. It's quite Ineffective. For about 15 bucks you can get one of these holding tank rinsers from Walmart (a little more at other places).

The statement that he "Never used the Black Tank" is erroneous. It may have been what he told you but it's a clear indicator that he didn't know how these things work, therefore also didn't know the proper way to use them. You may live in an RV like it's a house, but that don't make it a house. It is set up for a different lifestyle and therefore requires the occupants to adapt new habits. The black tank is in a direct line from the stool to the drain and (when properly hooked up) to the sewer/septic tank as well. When the valve is left open for a continuous drain, you never get the effect of a full clean out. He probably never put in the RV Toilet chemicals either...figuring it was a cost he didn't need since he had a septic hookup. RV Toilet chemicals are for a lot more than just odor control...that is probably the least important function they do. They also break down solids and help the flushing process when it's time to empty the tank. If chemicals were never used, you can bet that some of the solids, including paper, have hardened onto the tank floor and walls....so a good long soak may be necessary - with chemicals...but first you'll have to seal up the leaks or replace with a new back tank.

[rlhendren]

Originally Posted by RadioGuy

Any Leak in the black tank is a problem.

Thanks. I probably wasn't clear in my original post. The black tank doesn't leak. When I used the black tank flush, clean water ran from under the trailer around the sides of the belly pan in the area right below the black tank flush connection on the outside of the trailer.

As for the previous owner never using the black tank, I also wasn't entirely clear about that after re-reading my original post. Of course he used the toilet. What I meant was that he always had the sewer line in place with the black tank valve open and never filled the black tank. He said he always ran lots and lots of water during a flush to remove the solids. You are probably right about not using any kind of treatment either.

I'll get one of the tank flushing wands as well. Thanks for the link!

Ryan

[MelGoddard]

Originally Posted by KJRitchie

The backflow preventer is a cheap clear plastic device that breaks easily if not flush out with air over winter storage. Same thing happened to my preowned Classic 25fb the first time I used the black flush. I replaced the valve with an elbow fitting.

Kelvin

So WHERE is this "Backflow' Preventer"???
I have a copy of the water system blueprint for my 30' FC and cannot find such an 'animal'.
Nothing in the manual either.

Trailer Trash waiting for Spring to use my Tin Can Shed

[dkottum]

Originally Posted by MelGoddard

So WHERE is this "Backflow' Preventer"???
I have a copy of the water system blueprint for my 30' FC and cannot find such an 'animal'.
Nothing in the manual either.

Trailer Trash waiting for Spring to use my Tin Can Shed

The check valve is located just inside the external flush connection. It should self-drain after use to prevent freeze-up, but may not if mounted off-vertical or if the Airstream is parked a little nose-down. Or if the tank nozzles are plugged so the line cannot drain into the black tank.

[rlhendren]

Yes - like dkottum said - on the inside of the trailer at the same spot where the black tank hose connection is on the outside of the trailer. In my 23D, it's under the bathroom sink, easily visible by just opening the cabinet doors below the sink.