Is a vacuum breaker really needed?

[Double J]

Hi all! The sewer flush on my trailer has a vacuum breaker installed between the outside hose bib and the tank. Do I really need to have a vacuum breaker installed in this situation?

I am thinking about just using a check valve and getting ride of the part that could possibly flood water into my trailer. Any thoughts?

[Tim A.]

I strongly suggest leaving the vacuum breaker.

Your vacuum breaker protects the water supply you are hooked up to. That, of course, is in my own interest because I may be hooked up to the same system.

A check valve will not provide the same level of protection.

As an aside, the hose I use for our Sewer Solution has a check valve and a vacuum breaker. The belt and suspenders approach.

Tim

[Double J]

Thanks Tim! So do you have a vacuum breaker installed inside your trailer also?

I am not understanding how black tank water could possibly come up out of the tank to the hose bib, so I am not sure why it is needed. How would a vacuum be created by hooking up a hose to flush the black tank out? Maybe if I were to leave the hose attached and shut off the water, but this is the sewer flush out bib. A hose is only hooked up when flushing, usually at the dump station. It’s not like I hook up the fresh water hose to this at the camp site and leave it hooked up.

As a side note, I am totally new to Rv campers and have a lot to learn and do not have a complete understanding of all these systems. Please excuse my ignorance.

Thank you!

[uncle_bob]

Originally Posted by Double J

Thanks Tim! So do you have a vacuum breaker installed inside your trailer also?

I am not understanding how black tank water could possibly come up out of the tank to the hose bib, so I am not sure why it is needed. How would a vacuum be created by hooking up a hose to flush the black tank out? Maybe if I were to leave the hose attached and shut off the water, but this is the sewer flush out bib. A hose is only hooked up when flushing, usually at the dump station. It’s not like I hook up the fresh water hose to this at the camp site and leave it hooked up.

As a side note, I am totally new to Rv campers and have a lot to learn and do not have a complete understanding of all these systems. Please excuse my ignorance.

Thank you!

Hi

If you are at a full hookup campsite, do you wash down the black tank after you dump it? If so, where does that water come from? ... hmmm ....

If the black tank is *here* and the flush input is *there* which one is higher? It's going to depend a lot on how the trailer is leveled and a bunch of fiddly details.

In either case, any back flow can pull crud into a check valve. When it does, forget about that valve doing anything useful.

It very much does serve a purpose.

Bob

[Double J]

Thank Bob! I am not sure about how to use the sewer flush at the camp site. I have never camped in a camper that had a sewer flush and we have only dry camped with our airstream so far.

What your saying tho makes sense about how a back flow could happen depending on where the water source is relative to the tanks.

I don’t have any issue with using the vacuum breaker, but I have issue with where the overflow will go if there is a problem or malfunction. I don’t want the vacuum breaker inside the camper as that is obviously problematic and will lead to a flood inside the trailer someday.

Do you have a recommendation for how I could set up the vacuum breaker so that if it overflows, it will not do so inside my trailer? Should I just use a vacuum breaker attached to the hose like Tim above does? (Not sure if he has one in his trailer too tho)

Thanks!

[uncle_bob]

Originally Posted by Double J

Thank Bob! I am not sure about how to use the sewer flush at the camp site. I have never camped in a camper that had a sewer flush and we have only dry camped with our airstream so far.

What your saying tho makes sense about how a back flow could happen depending on where the water source is relative to the tanks.

I don’t have any issue with using the vacuum breaker, but I have issue with where the overflow will go if there is a problem to malfunction.. I don’t want the vacuum breaker inside the camper as that is obviously problematic and will lead to a flood inside the trailer someday.

Do you have a recommendation for how I could set up the vacuum breaker so that if it overflows, it will not do so inside my trailer? Should I just use a vacuum breaker attached to the hose like Tim above does? (Not sure it he has one in his trailer too tho)

Thanks!

Hi

Is this setup in an Airstream or is it in some other trailer?

Bob

[Double J]

Originally Posted by uncle_bob

Hi

Is this setup in an Airstream or is it in some other trailer?

Bob

It is a 2009, 25’ Flying Cloud Airstream.

[damonbeals]

If Airstream didn't think is was needed, or required by law you can bet they would not install it to save a buck.


Damon
#4827

[uncle_bob]

Originally Posted by Double J

It is a 2009, 25’ Flying Cloud Airstream.

Hi

There have been no reports of these things ever flooding a trailer. There's only water there when you do the flush. Lots of things break on an AS. Lots of things cause problems for folks. This is one that never comes up as a problem.

If indeed you want to do something, remove the entire flush system. Simply cap off the hole in the black tank. You can then manually flush the tank (hose and spray wand down the toilet). That will avoid any issues with the flush input. I would not use the flush setup without all the proper parts being in place.

Bob

[Double J]

Originally Posted by damonbeals

If Airstream didn't think is was needed, or required by law you can bet they would not install it to save a buck.


Damon
#4827

Thanks! It’s not that I don’t think it is needed, especially after what Bob said, it’s that I don’t want it so that if it backflows or malfunctions, it purges the liquid into my trailer. I am really more concerned about the vacuum breaker malfunctioning and spilling fresh water all up in my trailer when I am trying to to a sewer flush. Looking at how the device works, it seem like that is a good possibility of happening. The one I pulled out of my trailer did not seal well and water easily flowed out the purge part with the stopper pushed all the way up.

[Double J]

Originally Posted by uncle_bob

Hi

There have been no reports of these things ever flooding a trailer. There's only water there when you do the flush. Lots of things break on an AS. Lots of things cause problems for folks. This is one that never comes up as a problem.

If indeed you want to do something, remove the entire flush system. Simply cap off the hole in the black tank. You can then manually flush the tank (hose and spray wand down the toilet). That will avoid any issues with the flush input. I would not use the flush setup without all the proper parts being in place.

Bob

Was reported on post 21 in this thread and I think a few other places in that thread. Also read somewhere that a guy had his wife watch the vacuum breaker when he flushed the system incase it overflows as he has the same concern.
https://www.airforums.com/forums/f44...-188713-2.html

(Edit: just did a google search for “rv vacuum breaker flood” and, uh, ya, seems to be a real issue. Unless airstream uses their own proprietary vacuum breakers, chances are they will have the same issues as other trailer manufactures.)


Also, like I just mentioned, the vacuum breaker I just pulled out did not seal correctly and was letting water out the purge part. If the my plex pipe was not clogged in my trailer then I would have had water spewing inside the closet of my trailer just like in that post.

Regardless of all that, it is my understanding that the if there is a backflow of black water heading to the fresh water hook up, then this vacuum breaker would purge the black water inside my closet. So if this device is needed to prevent backflow, it will do so by flooding my trailer with black tank water.

Is this correct in how this system is supposed to work?

[uncle_bob]

Originally Posted by Double J

Was reported on post 21 in this thread and I think a few other places in that thread. Also read somewhere that a guy had his wife watch the vacuum breaker when he flushed the system incase it overflows as he has the same concern.
https://www.airforums.com/forums/f44...-188713-2.html

Also, like I just mentioned, the vacuum breaker I just pulled out did not seal correctly and was letting water out the purge part. If the my plex pipe was not clogged in my trailer then I would have had water spewing inside the closet of my trailer just like in that post.

Regardless of all that, it is my understanding that the if there is a backflow of black water heading to the fresh water hook up, then this vacuum breaker would purge the black water inside my closet. So if this device is needed to prevent backflow, it will do so by flooding my trailer with black tank water.

Is this correct in how this system is supposed to work?

Hi

No, that's not at all how it works. It simply lets air into the line so that there is no siphon effect. A siphon depends on a vacuum. Break the vacuum and the process stops dead in it's tracks.

There are multiple potential issues with every device in an RV. If this really bugs you, remove the entire system. There is a long list of other far more common things that also will take off the worry list. The tradeoff is a bit more work flushing the tank.

Bob

[Wayne&Sam]

You can always buy a vacuum breaker that connects to the ens of your hose. Just make sure you always use it.

In 14 years I haven't had a problem with the breaker airstream installed. If it did fail, it would only be a problem while flushing the black tank and I'm sure you would notice a difference in the sound. I usually start flushing and then if I think I hear a weird noise I check inside to be sure all is ok (instead of just standing around doing nothing).

Be sure you blow it out when winterizing. I'm thinking not doing that may be much of the problem.

[Double J]

Thanks all! Looks like I will be getting a vacuum breaker for the hose as it is by far the best way to go. According to the install instructions for inline vacuum breakers it states:
“Vac/Check cannot be installed in an inaccessible location where venting of water from device during normal operation causes damage.”

I do not think airstream has done a proper job of installing the vacuum breaker in my trailer as while the device is accessible, the water it may vent during normal operations will not be. I would have no way to reach where the water will end up to try and dry it out and the water would cause damage.

Given the immense amount of reported issues with vacuum breakers on various RV forums, the fact that vacuum breakers can “vent water during normal operations” and that I am all about an ounce of prevention, it is clear the best thing to do is to add a vacuum breaker to the garden hose and remove the device that will at some point cause water damage inside the trailer.

When reading more about vacuum breakers from the manufactures web sites I see that they say over time the device will need to be replaced as seals and other parts will wear out. Given that this device is really not needed to be installed inside the trailer, the most conservative thing to do would be to use a garden hose vacuum breaker as some day they will all leak.

[KTD]

2019 FC 23 FB---Hooked up hose to dump my black tank which was only 25% full. Hooked up my garden hose to the tank flush input. Turned on water source and as I walked to the trailer noticed water coming out of the bottom of the trailer around the trim ring for the back tank drain. Immediately shut down water flow. Water drenched my heater control board and the heater was trying to ignite even though the thermostat was off. Pulled the power to the board. That thankfully has dried out and the heater is working.

It seems the back flow preventer or vacumm breaker failed. After pulling gate valve and dumping tank I again turned on water and things seem to be fine-no more water flow inside the trailer.

Debating on weather I should replace the breaker in which case I have to cut out some of the cabinet backer to get to it or to wait and see if this problem reoccurs in spring. Any comments or suggestions would be appreacitated. By the way does anyone know what the cabinet backer material Airstream uses is called. I would imagine I could pick up a piece at the local lumber supply.

Thanks in advance for any input anyone can provide.

[Belegedhel]

It is interesting to see this reference to "water from device during normal operation." I would think that if a vacuum breaker is functioning normally, then water is coming from the outside of the trailer, through the vacuum breaker, and into the black tank. If, for example, you were running water into your black tank and suddenly a fire truck attached to the water main next door to you and started pumping so much that there is not only no water flowing into your tank, but it is pulling a vacuum and potentially sucking contaminated water out of your tank and into the water system, the vacuum breaker would function by stopping backflow and opening the system up to suck in air. So, not understanding this release of fluid under normal operations...

Now, I have seen vacuum breakers fail that protect household lawn sprinkler systems. This can happen when someone fails to winterize the system, leaves pressurized water attached to the vacuum breaker, and the water inside the vacuum breaker freezes causing the plastic bits in the vacuum breaker to break, and a fountain of water pouring out the vacuum breaker results. I suppose any time a vacuum breaker fails, you could get this kind of leak, but I would not call that "normal" operation, I would call that a failure.

On a similar note, I was installing an outdoor shower on my trailer recently, and discovered that the manufacturer of the outside shower had gone the extra mile to put a vacuum breaker between the shower head and the mixing valve. As I was screwing the shower head hose onto the vacuum breaker, it came apart in my hands. Again, had this part failed at some point in the future, the leak would have been to the interior of my trailer. I looked at dozens of other outdoor shower assemblies and didn't find a one with a vacuum breaker integrated into it.

Again, it seems like a "best practice" would be to have a pressure regulator and vacuum breaker installed upstream of your potable water hose. I would be surprised if a vacuum breaker isn't already a permanent part of the shore water faucet as well.