Most times it is under the bathroom sink, but others have found it in the wall behind the bathroom or in a closet next to the bathroom. If it's not under the sink, look for an access panel on an outside wall to the bathroom.
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Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, replaced chairs, sun screens, added awnings, etc.
Mine is behind the wall of my wet bay, right after where the hose hook-ups. I have to remove the wall inside the pass through to gain access to the back side of the wet bay. The anti-siphon valve is for the black tank. The only thing under my bathroom sink is the air-admittance valve which is part of the bathroom sink - grey water holding tank system.
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Who you are right now is a sum total off all you use to be.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually
Biker Bill -i have basically the same unit as yours and I went out looking for the thing (because I know my day will come when I need to fix it). Well I did not find it. The only place I did not look was behind the convenience center (mainly because my basement compartment is full of stuff and I did not want to take it all out and look behind the bulkhead panel for the convenience center). It must be there.
I did NOT find it...
Under the double sink in the main front bath
Under the sink in the half bath
Under the kitchen sink.
Sorry!
I did see this mystery access door in a closet/cabinet in the front bath (see pic - little black square behind the clothes hanger).
I have no idea what that access door is for.
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MikenDebbie Aggie ‘77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy
Wherever you are looking, the backflow/air break valve has to be installed above the level of the rim of the toilet bowl. That’s why it can be installed just below the sink counter top in the bathroom. On our rig, the valve is installed in the pocket door space between the shower wall and the pantry cabinet.
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Bob & Becky
2012 3402RL
2012 Chevy 2500HD D/A CC 4WD
That makes complete sense - I will look again tomorrow! Thanks Rohrmann!
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MikenDebbie Aggie ‘77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy
I'm glad somebody with my model responded. When one of finds it we will have to pass the info along or maybe somebody else with our model will give us a answer. I too checked under all sinks.
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Bill M Apache junction az winter, Show Low Az summer 2019 3930fb
On my SOB trailer, when I am using the Black Tank sprayer, you can here the water running thru the back flow device, that might give you a head start in looking for it.
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Kevin in Quartzsite, Arizona....It's an experience!
Look around in your storage areas under the bathroom area floor. Look for 4 pipes going up thru the floor where there should only need to be 2, one for hot and one for cold. The two extra are likely to the anti siphon flush valve. That is how I determined mine was in the wall between the shower and my entry closet. I also have an access panel in the back of the closet wall. It was not located over that valve though. I could reach in and down and to the left a feel it. I had to cut a new opening there. You can see that panel in the upper right and the new opening lower left (Note that I removed my valve). I used the piece I cut out, made a picture frame for it, and used that as my new cover.
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Bill & Patricia
Riley, our Golden
2007 3075RL (recently sold, currently without)
BB_TX is on the right track. I removed the black plastic access hatch in the lower closet in the front bath and there it was! see pics. Many thanks to Rohrmann for the hint in post #6...and I anticipate having to enlarge the access hole (just like BB_TX did) when my day comes!
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MikenDebbie Aggie ‘77 in the sticks near Austin TX
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Aussie Gus + Texas Heeler Jimmy
There are 2 different anti-siphon valves in our 2020 3931FB (2 different black tanks). MikenDebbie is correct, the forward one is inside the wall, front bathroom, lower cabinet. The rear one is under the bed, a hole is cut in the floor, but why I don't know because the bed would have to be removed to access it. It can be seen if you look over the top of the wall in the basement behind the convenience center. The pex tubing is white (non-potable) to these valves, all other pex is either blue or red (cold or hot potable).
I removed the access panel in the bathroom and enlarged the hole in the wall so that i could see it better and look at it every time I flush the tank. I also use a flashlight to look at the other one each time as well.
OK, I'm not up to date on this conversation. What is the issue that causes you to need access? do the break, leak,..... ? Sorry this sounds important to know and I don't want to find out in an emergency. One year into having a 5er needing to learning what I can
OK, I'm not up to date on this conversation. What is the issue that causes you to need access? do the break, leak,..... ? Sorry this sounds important to know and I don't want to find out in an emergency. One year into having a 5er needing to learning what I can
The ones installed in Montanas, and probably all others, are very cheap plastic anti siphon atmospheric vent valves. And are prone to leaking and flooding your floor. Brass replacement valves are available, but I don’t know how much better they are. The valves have a vent to air that is suppose to close when the water is turned on, and open back to air when turned off, and will leak if they fail to close and seal properly. Some who had them leak found that a bug had crawled into the vent and prevented the valve from sealing. I don’t know if any of them have a screen to keep bugs out.
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Bill & Patricia
Riley, our Golden
2007 3075RL (recently sold, currently without)
BB_TX is on the right track. I removed the black plastic access hatch in the lower closet in the front bath and there it was! see pics. Many thanks to Rohrmann for the hint in post #6...and I anticipate having to enlarge the access hole (just like BB_TX did) when my day comes!
I would not wait. As a matter of fact I did not wait.
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Mocha, one-eyed toothless, hurricane survivor, Pirate dog
2019 20th Anniversary Edition 3701LK
B&W 20K for Ford OEM Puck
2018 Ford F-350 Lariat CCLB PSD DRW KJ5CQH
Don't bet on the color of the PEX to locate one of these valves. All PEX is used for potable water, white, red, or blue, doesn't matter. On our rig, they used red PEX for the black tank rinser line, all the way from the convenience center. The one photo shows the red line at the bottom of the photo that is the black tank rinse line from the fitting on the back of the convenience center wall. The next photo shows the rinse line where it enters the front of the black tank, and the other photo shows the valve in the pocket door space between the shower and the back of the pantry cabinet.
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Bob & Becky
2012 3402RL
2012 Chevy 2500HD D/A CC 4WD