Can anyone tell us what these two white water lines are for? At least, we assume they are water lines. They are found under one of the sinks in the bathroom vanity. Thank you.
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Larry & Paula
2024 Montana High Country 331RL
Based on my reading the forum - those are notorious for failing and flooding your RV. Many folks replace them with brass vacuum breaker (similar to the pic below) or cut the thing out and simply tie the lines together permanently. I have not yet replaced my two vacuum breakers (I have two black tanks) but it is on the list.
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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
That is the check-valve for your black tank flusher. You attach a garden hose to your black tank flusher in your convenience center and turn shore water spigot on. Water flow through a separate water line (the white line). It will travel through that pipe under your sink. That black "thing" is a check valve, which allows water to flow only one direction. This way, there is never any back-feed from the black tank that could feed backwards from the black tank BACK into the garden hose or worse, back into the campground (or your hosue) water system.
It is important to have that check valve in place, but sometimes when they fail, folks will remove them completely (not a good idea though). Others will be a little beefier model, like the one pictured above in the prior post.
But, that is what the white pipes and and black "thing" connected to them is.
The only time you'll have water in that line is when you flush your black tank via the black tank flush hook-up in your convenience center. And yes ... when you winterize, you do need to either run some RV pink stuff antifreeze through that line, or at best, blow it out. It does hold water and it will freeze up and break if not winterized, just like the rest of your water lines.
Happy camping!
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History is not about the past, it's an explanation of the present.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually
I think many of these fail because people aren't using pressure regulators when they flush their black tank. I've seen a number of people (and I've done it too) just hook the hose up and let 'er rip. I thought mine was failing because it started leaking then realized I was putting unregulated pressure through it. Remember, these are the same quality as other plumbing components in your trailer.
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Dave and Samantha, Full-Time since 2020
2024 Montana Legacy 3941FO
2024 RAM 3500 Laramie Night Edition
OK.... now I'm embarrassed I've been here a while and read a lot about this. I didn't know it's location or the potential fubar it could cause. I thought it would back flow at the convenience center. Going to upgrade, I back flush a lot! And this could also cause black tank odor?
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Tony & Donna & the best dog ever, Murphy.
2022 Montana HC, 295RL, 720 watts Solar, Onan 3600 LPG, 2K inverter, 200AH Lithium. 2020 GMC Denali 2500 6.6 Duramax, Demco 21K Auto Slide
Be glad yours is under the sink. Mine was in the wall between the shower and the entry closet. And it started leaking. Bad. Had to cut an opening in the back of that closet to get access to remove that antisiphon/vacuum breaker valve. Connected the pipes together and added an external vacuum breaker valve.
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Bill & Patricia
Riley, our Golden
2007 3075RL (recently sold, currently without)
Below is rough schematic for where my vacuum breakers are located. If you don't know where your vacuum breakers are located - look for them so you know where they are just in case. The one I colored red will flood the basement if it goes bad. The one I colored green will flood our front bathroom and bedroom if it goes bad.
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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
Jdarwin (2019 3931FB) shows photos of the vacuum breaker located behind the basement wall near the back of the wet bay in post #18 in this thread from April 2022. In post #19 I show the location of the 2nd vacuum breaker. Look for an access hatch in the lower closet.
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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
We know all about back flushing the black tank as we've owner motorhomes for 13 years, but just hadn't run across anything like what I posted in my opening post.
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Larry & Paula
2024 Montana High Country 331RL
That is the check-valve for your black tank flusher. You attach a garden hose to your black tank flusher in your convenience center and turn shore water spigot on. Water flow through a separate water line (the white line). It will travel through that pipe under your sink. That black "thing" is a check valve, which allows water to flow only one direction. This way, there is never any back-feed from the black tank that could feed backwards from the black tank BACK into the garden hose or worse, back into the campground (or your hosue) water system.
It is important to have that check valve in place, but sometimes when they fail, folks will remove them completely (not a good idea though). Others will be a little beefier model, like the one pictured above in the prior post.
But, that is what the white pipes and and black "thing" connected to them is.
The only time you'll have water in that line is when you flush your black tank via the black tank flush hook-up in your convenience center. And yes ... when you winterize, you do need to either run some RV pink stuff antifreeze through that line, or at best, blow it out. It does hold water and it will freeze up and break if not winterized, just like the rest of your water lines.
Happy camping!
Don't want to hijack the thread but I have a related question. I have a 2013 3582RL. The last time I tried to do a black tank flush water would not enter the white line. It pressurized but wouldn't go into the black tank. Could a bad check valve cause this? My check valve is under the sink in our bedroom.
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Cal & Kim
2013 3582RL
2012 Ram 3500 Laramie
I had an antisiphon valve leak years ago. But mine leaked because it was cracked. Unlike most all others I have seen, mine was clear plastic, so I could see thru it to the moveable “valve” inside. And it was just like the diagram I posted above. The moveable part was not spring loaded to hold it closed when not in service. It just fell to the closed position due to gravity. And there was no rubber seal to hold it watertight when not in service. Or for the moveable part to stick to and prevent it from opening under water pressure. Maybe the newer ones are different, but I don’t see any way the one I had could have ever completely blocked water flow.
If I remember correctly my hose connection in the convenience center had a check valve in it. If yours does, that could also be stuck.
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Bill & Patricia
Riley, our Golden
2007 3075RL (recently sold, currently without)
Madmax - I think it was my 2006 that had the valve under the sink. I had a problem but don't remember what !!! I think it wouldn't flush. My valve was just a plastic type fitting that was threaded together, so I just unscrewed it. Inside was a marble thing that plugged the pipe when pressure came the back way. I just removed the marble and all was well. I could use an external back flow device to accomplish the same thing.
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Tom and Gail
2013 Mountaineer 362
2012 Silverado 2500
Update - So I decided to connect the two lines together and then add an external check valve. I connected the hose to the tank flush in the convenience center. I knew water was coming in as the hose filled. I looked under the sink where I joined the 2 lines. I knew water was getting to the point of the connection because I had a very slow drip at one of the connections.
However, water is still not entering the black tank. I'm not sure what to do at this point. What can I be doing wrong? Anything I may not have thought of? Thanks.
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Cal & Kim
2013 3582RL
2012 Ram 3500 Laramie