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Old 04-15-2020, 02:53 PM   #1
rvsareus
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Water problem.

I have a 2019 381 th and was flushing the black tank the other day with the tank rinse when water came from under the bathroom sink and floode some things. Shut it down and cleaned up. Thank god it was just clean water. Is that valve under the sink no good?
 
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Old 04-15-2020, 03:13 PM   #2
BB_TX
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The infamous black tank flush anti siphon valve. Yes, they are a high failure item. Some have replaced those cheap plastic things with better quality brass ones. Some have removed the valve, connected the pipes together, and use an external anti siphon valve.

Just be glad yours is under the sink and not inside a wall like mine was. And notice I did say “was”.
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Old 04-15-2020, 04:09 PM   #3
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Thanks for the info guy, I will replace it with something much better.
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Old 04-15-2020, 05:24 PM   #4
CFDFireman90
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That is what I did. Never had it happen to me but read about it happening to a lot of others. Get rid of it, use a check valve that attaches to the hose when you hook it up.
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Old 04-15-2020, 06:51 PM   #5
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What they said!!! Mine did leak. I took it out and looped the pipe in storage bay. Mine already had a check valve in the convenience center!
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Old 04-15-2020, 06:57 PM   #6
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Some have taken then out and thrown them away. I replaced mine with a one way valve. It’s a safety device to prevent water from entering the water hose if the water pressure should go to zero while you are cleaning your black tank. What are the chances of that? So close to zero I wouldn’t worry about it.
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Old 04-16-2020, 08:11 AM   #7
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I have not changed mine YET, but I can see both of them and I check them as I flush each time. I am not looking forward to changing them because even though I can see them, I don't think I can easily get to them. But I do have the PEX tool and on some days I am up to a challenge, but most days not.
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Old 04-16-2020, 03:04 PM   #8
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Now wait a minute. This does not sound right at all. If you were running water via the black tank flusher, you had a water hose connected to the black tank flush connection in your wet-bay, right? Yours is a Montana 2019 381 Toy Hauler, Right?

OK, Looking at the floor plan, the bathroom sink is in the middle of the trailer. The anti-syphen valve everyone is talking about is attached to your black tank flusher line which runs from your wet bay to your black tank (only 1 dedicated line). The anti-syphen valve is located right behind the wall of your wet bay, NOT under your bathroom sink.

The valve everyone is talking about is the Air Admittance vent under your bathroom sink. This vent is connected to your grey tank (usually) so the tank will not create a vacuum when filling or dumping.

The black tank flusher line does not run under the sink. My previous Outback travel trailer had the black tank flusher line run under the sink, only because the garden hose attachment was actually inside the cabinet that supported the sink. The garden hose attachment was directly under the sink, on an outside wall. The line ran directly to the black tank anti-syphen Check Valve.

If that valve fails, water does not flow anywhere, unless the actual connection is broken, or leaking. Then you could have water spewing (which actually happened to my Outback)

This is the air admittance valve under your sink that vents the grey tank:



This is what the black tank flusher anti-syphen check valve looks like:



I would sooner believe, you overfilled the black tank when you ran your black tank flusher. Your bathroom sink is plumbed into your black tank (right, wrong, or indifferent, its plumbed into the black tank). When the black tank filled, water flowed backward from the air admittence valve. It failed.

Let's get the terms and definitions correct here, and let's get the water flowing the right way.
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Old 04-16-2020, 05:49 PM   #9
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Originally Posted by DutchmenSport View Post
........

OK, Looking at the floor plan, the bathroom sink is in the middle of the trailer. The anti-syphen valve everyone is talking about is attached to your black tank flusher line which runs from your wet bay to your black tank (only 1 dedicated line). The anti-syphen valve is located right behind the wall of your wet bay, NOT under your bathroom sink.
............
Actually many people have found the anti siphon valve under their sink. Yes, the one in your second picture. Mine was inside the wall between my shower and the entry closet on opposite side of trailer from the wet bay/convenience center.
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Old 04-26-2020, 02:39 PM   #10
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The two pictures are showing two different things, #1 is a VENT, #2 Is the anti-siphon valve in line to the black tank. There's also a vacuum Breaker at the convenience center.



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Old 04-26-2020, 06:00 PM   #11
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I have had 6 campers. That anti syphon valve has failed on virtually every rig, no mater what it was made of or who made it. To break a syphon it has to be open to the air and thus, a leak results in a flood while flushing. Until they make a sealed unit with a vent to the outside, I will remove it and bypass it.
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Old 04-26-2020, 08:44 PM   #12
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My anti-siphon valve is located in the lavitory cabinet in my bathroom. I have a 2010 Mountaineer. I noticed a leak into our garage after about the 4th or 5th time we drained the tanks. I had a wye at the outside faucet with a line running to my fresh water and one to the backflush. When done draining the tanks I would turn off the side of the wye that was connected to the backflush but I didn't disconnect the hose to the backflush. As the pressure started to reduce in the backflush line a little water would go thru the discharge side of the anti-siphon valve . The solution was to disconnect the backflush hose from the RV and let the water drain back out of the RV. This would be the water from the backflush connection to the anti-siphon valve. After that water drained, I reconnected the hoses for next use. That was 10 years ago. Hasn't leaked since.
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Old 04-27-2020, 07:08 AM   #13
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Quote:
Originally Posted by BB_TX View Post
The infamous black tank flush anti siphon valve. Yes, they are a high failure item. Some have replaced those cheap plastic things with better quality brass ones. Some have removed the valve, connected the pipes together, and use an external anti siphon valve.

Just be glad yours is under the sink and not inside a wall like mine was. And notice I did say “was”.
Yeah, we just ordered a copper one too. No leak so far, just doing as a preventative from reading everyone else's posts.
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Old 04-27-2020, 09:25 AM   #14
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Now that it has come to my attention, I located mine while the black tank flush was running. A couple drops of water on the hose. Mine is crimped in place, not attached with screw connections. Is the consensus that the safest thing to do is remove the back-flow preventer and replace it with a "U" connection? Does use of the PEX tool need some practice or is it first time works, for someone used to crimping electrical connectors?
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Old 04-27-2020, 10:43 AM   #15
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Now that it has come to my attention, I located mine while the black tank flush was running. A couple drops of water on the hose. Mine is crimped in place, not attached with screw connections. Is the consensus that the safest thing to do is remove the back-flow preventer and replace it with a "U" connection? Does use of the PEX tool need some practice or is it first time works, for someone used to crimping electrical connectors?
Pex crimping is easy. Just get the tools. Pex crimper, pex crimp ring removal tool, pex cutter.

I cut my backflow preventer loose in the basement and capped it off, no need still having the pipe under the sink.

Now I use one that just screws on the hose.
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Old 04-28-2020, 08:59 PM   #16
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Show a pic of back flow valve you put on hose
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Old 04-29-2020, 08:16 AM   #17
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Show a pic of back flow valve you put on hose
This is the type I use.

https://www.lowes.com/pd/Arrowhead-B...reaker/3695370

There are some cheaper ones that are also listed as vacuum breaker, but not listed self draining. But I bought the one above for a little more.
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Old 04-29-2020, 11:11 AM   #18
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This is the type I use.

https://www.lowes.com/pd/Arrowhead-B...reaker/3695370

There are some cheaper ones that are also listed as vacuum breaker, but not listed self draining. But I bought the one above for a little more.

Thx for posting! I'm getting one.
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Old 04-29-2020, 11:17 AM   #19
Biker bill
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Thanks, do I disconnect the built in one or use it with the built in one. 2019 3930 fb.
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Old 04-29-2020, 11:51 AM   #20
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Thanks, do I disconnect the built in one or use it with the built in one. 2019 3930 fb.
There is no need to use an external one unless you remove the built in one.
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