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Old 07-18-2020, 06:31 PM   #1
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vent in bath spurting water when black tank flush used

We have a 2017 cedar creek silverback 33ik. I have been using the black tank flush system without incident since new.

Today I went through the dump procedure as usual. However when I put pressure to the black tank flush system, water (fresh) began spurting from what I believe to be a vent of some sort connected to the drain system under the sink in the bath.
Has anyone had this issue and what was the fix

Thanks for your help in advance.
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Old 07-18-2020, 06:36 PM   #2
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Was your black tank waste gate valve open?
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Old 07-18-2020, 07:04 PM   #3
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Originally Posted by kurtkraly View Post
We have a 2017 cedar creek silverback 33ik. I have been using the black tank flush system without incident since new.

Today I went through the dump procedure as usual. However when I put pressure to the black tank flush system, water (fresh) began spurting from what I believe to be a vent of some sort connected to the drain system under the sink in the bath.
Has anyone had this issue and what was the fix

Thanks for your help in advance.

My understanding is that the valve you are talking about is a back flow prevention valve. From my reading, they are normally located under a bathroom sink. It is supposed to close when water is flowing in the correct direction. It should open to atmosphere and close from the destination of the water flow to prevent a siphon from pulling water backwards.
These are common valves and can be purchased at most home improvement stores.
Should be a relatively easy replacement. Just make sure to install with the correct water flow direction!
BTW, having your black tank valve open or closed shouldn't have any impact on this valve. The normal black tank vent will prevent any pressure build up. BUT, if you leave it closed too long, you WILL have a fountain on your roof!
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Old 07-18-2020, 08:10 PM   #4
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I have a brass elbow ready to replace that piece of junk.
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Old 07-18-2020, 09:13 PM   #5
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I have a brass elbow ready to replace that piece of junk.

Bought an used camper and was checking the black tank flush. My backflow valve failed and flooded the inside of the camper. A couple quick connect elbows and a small piece of PEX and thatíll never happen again!!
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Old 07-19-2020, 06:36 AM   #6
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I have a brass elbow ready to replace that piece of junk.
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Bought an used camper and was checking the black tank flush. My backflow valve failed and flooded the inside of the camper. A couple quick connect elbows and a small piece of PEX and thatíll never happen again!!
This is a very irresponsible and potentially hazardous thing to do. Doing this has the potential of killing people. You should never, ever eliminate a backflow preventer, especially in a cross connection situation such as this.

I will direct you to this thread where you might learn what I am talking about:

https://www.forestriverforums.com/fo...ns-191907.html

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Old 07-19-2020, 07:22 AM   #7
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Can you just put a back flow preventer on the hose and call it a day?
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Old 07-19-2020, 07:31 AM   #8
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Can you just put a back flow preventer on the hose and call it a day?
No.

Different backflow devices have different, specific purposes. They are all designed for different levels of protection. A cross connection is one of the most serious and dangerous types of situations where you can never be careful enough. Substituting a cross connection prevention device such as those installed on black water tank flush systems with a simple backflow preventer is not acceptable or permissible.

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Old 07-19-2020, 07:38 AM   #9
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I have a brass elbow ready to replace that piece of junk.
That is putting a penny in a fuse box.
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Old 07-19-2020, 07:47 AM   #10
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I have a brass elbow ready to replace that piece of junk.
You really should think about the risk you impose on others by doing this. Iím confused by your plans to do this because of something you said in another thread. This is what you said:

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Wearing a mask does not prevent you from getting it...it prevents you from spreading it.


That's why I won't go into a place of business if the employees aren't wearing masks. My mask that I am wearing is protecting them from me. The fact that they aren't wearing masks is the risk to me.
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Old 07-19-2020, 07:54 AM   #11
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You really should think about the risk you impose on others by doing this. Iím confused by your plans to do this because of something you said in another thread. This is what you said:



Bruce
Good analogy. One significant difference: Others cannot protect themselves if someone contaminates the water supply, short of not using the supply. So, taking off backflow protection is FAR worse!
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Old 07-19-2020, 08:13 AM   #12
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The air flow admittance valve is there for a very simple reason and should not be disabled in any way. The number one rule for plumbing is that you have air (vent) behind water so that the water will drain out well. If you disable the AAV then you have no air behind the water so that it will drain well. If you do not believe me try this simple example, take a clear milk jug and fill with water over the sink turn the jug upside down so that it will drain. The water will come out in short glugs because there is no air behind the water to allow a proper drain. Now refill the jug with water, turn it over again and carefully puncture the bottom of the jub with a knife or similar. You will be able to observe that the water will drain much smother with a vent.
Same concept applies to your tank.
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Old 07-19-2020, 08:28 AM   #13
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The air flow admittance valve is there for a very simple reason and should not be disabled in any way. The number one rule for plumbing is that you have air (vent) behind water so that the water will drain out well. If you disable the AAV then you have no air behind the water so that it will drain well. If you do not believe me try this simple example, take a clear milk jug and fill with water over the sink turn the jug upside down so that it will drain. The water will come out in short glugs because there is no air behind the water to allow a proper drain. Now refill the jug with water, turn it over again and carefully puncture the bottom of the jub with a knife or similar. You will be able to observe that the water will drain much smother with a vent.
Same concept applies to your tank.

I donít believe the issue he is having is the AAV, but rather the anti-siphon/backflow valve for the black water flush.
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Old 07-19-2020, 09:02 AM   #14
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Originally Posted by clr View Post
The air flow admittance valve is there for a very simple reason and should not be disabled in any way. The number one rule for plumbing is that you have air (vent) behind water so that the water will drain out well. If you disable the AAV then you have no air behind the water so that it will drain well. If you do not believe me try this simple example, take a clear milk jug and fill with water over the sink turn the jug upside down so that it will drain. The water will come out in short glugs because there is no air behind the water to allow a proper drain. Now refill the jug with water, turn it over again and carefully puncture the bottom of the jub with a knife or similar. You will be able to observe that the water will drain much smother with a vent.
Same concept applies to your tank.
The air admittance is only on the input side of an rv vacuum breaker-check valve. The output side of the valve has a spring loaded check (ball) valve and the input side does have an ambient opening that is sealed off via free floating plunger when pressure is applied and when pressure is removed allows the plunger to fall as water empties the valve cavity and input tubing and again seals off the input side. This is what one sees when the hose is disconnected from the external black tank flush port and the water that runs from the port. The residual water in the valve output tubing side, which is sealed by the spring loaded check valve at the valve output port, drains into the empty black tank, which is vented to ambient, through the tank flush nozzle.
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Old 07-19-2020, 09:24 AM   #15
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The way a factory has to install the black tank flush plumbing (routed up through floor minimum 6" above toilet seat level) and the vacuum breaker-check valve fails I would just install a bypass at the valve location. My valve is in the washer/dryer closet 5 feet above floor level.
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Old 07-19-2020, 09:51 AM   #16
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I would just install a bypass at the valve location.
What does this mean?

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Old 07-19-2020, 10:18 AM   #17
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Good analogy. One significant difference: Others cannot protect themselves if someone contaminates the water supply, short of not using the supply. So, taking off backflow protection is FAR worse!
I didn't put the siphon break on my dishwasher either when I installed it..goes right to the garbage disposal.

I knew a few people who read my solution would make their heads explode. I run my black tank flush for 5 minutes with the valve open. The sprayers are not submerged in any liquids in the tank. And, the water supply would have to all of a sudden fail and pull a vacuum.
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Old 07-19-2020, 10:39 AM   #18
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Originally Posted by kurtkraly View Post
We have a 2017 cedar creek silverback 33ik. I have been using the black tank flush system without incident since new.

Today I went through the dump procedure as usual. However when I put pressure to the black tank flush system, water (fresh) began spurting from what I believe to be a vent of some sort connected to the drain system under the sink in the bath.
Has anyone had this issue and what was the fix

Thanks for your help in advance.
The OP clearly stated that the valve in question is on the drain system under the sink and not the supply side. So he is clearly not talking about a back flow prevention valve.
Also he stated that the valve in question is under the bathroom sink this is the normal location for the air admittance valve.
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Old 07-19-2020, 10:47 AM   #19
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The OP clearly stated that the valve in question is on the drain system under the sink and not the supply side. So he is clearly not talking about a back flow prevention valve.
Also he stated that the valve in question is under the bathroom sink this is the normal location for the air admittance valve.
It happened while he was flushing his black tank.
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Old 07-19-2020, 11:19 AM   #20
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What does this mean?

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